JP7605904B2 - High power ion beam generator system and method - Google Patents

Description

This application claims priority to U.S. Provisional Application No. 62/447,685, filed January 18, 2017, which is incorporated herein by reference in its entirety.

(Field)
Provided herein are high energy ion beam generator systems and methods that provide low cost, high performance, robust, consistent, uniform, highly efficient, and high current/high to medium voltage generation of neutrons and protons. Such systems and methods find application for commercial scale generation of neutrons and protons for a wide variety of research, medical, security, and industrial processes.

(background)
A particle accelerator is a device that energizes ions and drives them into a target. A neutron generator is a specific application of a particle accelerator that produces neutrons by fusing isotopes of hydrogen. A fusion reaction is carried out by accelerating either deuterium, tritium, or a mixture of the two isotopes into a target that also contains deuterium, tritium, or a mixture of the isotopes. The fusion of deuterium atoms results in the formation of ^3He ions and neutrons half the time, and the other half results in the formation of ^3H (tritium) ions and protons. The fusion of deuterium and tritium atoms results in the formation of ^4He ions and neutrons.

Particle accelerators and neutron generators have numerous applications in medicine, imaging, industrial processes (e.g., online analyzers, metal cleanliness, raw materials, Al-based catalysts, energy production), materials analysis, safety measures (e.g., nuclear material detection), research, education, exploration, security (e.g., explosives detection, chemical weapons detection, contraband detection), and ion implantation.

Historically, neutron generation has employed approaches that either involve very complex and expensive systems, generate or use excessive levels of hazards, or provide insufficient neutron output to meet commercial needs. Radioactive sources capable of producing high neutron levels contain harmful amounts of radiation, requiring many safety considerations. Neutrons can also be produced by nuclear reactions using accelerators (e.g., cyclotrons, van de Graaff accelerators, LINACs), with large yields but at substantial cost and operational complexity. The use of neutron generators using the deuterium-tritium (DT) reaction has addressed some of the safety issues, but due to the tritium content, they required sealing and typically had a short lifespan. Attempts to use deuterium-deuterium (DD) neutron generators have had limited success due to the approximately 100-fold lower fusion cross section of the DD reaction compared to the DT reaction.

The cost, lack of efficiency, safety concerns, and lack of durability of existing systems have prevented them from finding use in many commercial applications that could benefit from neutron generators. Addressing these issues in this field has become so complex that routine optimization or modification of existing systems has failed to provide meaningful or practical solutions.

Provided herein are high energy ion beam generator systems and methods that provide low cost, high performance, robust, consistent, uniform, low gas consumption, low fuel consumption, and high current/high to medium voltage neutron and proton generation. The systems and methods provide a balance of throughput, cost, and reliability not previously achieved. Such systems provide viable commercial scale neutron and proton generation for commercial processes such as semiconductor and LED manufacturing, among others.

Described herein are multiple performance enhancing technologies that individually and collectively contribute to high performance high energy ion beam generator systems and methods. Unless expressly stated otherwise or contrary to logic, it should be understood that each of the technologies described herein may be used in combination with one another to provide a generator with desirable performance features and characteristics. The technologies are conveniently grouped into the following categories: I) Ion Source Technologies, II) Infrastructure Technologies, III) High Voltage System Technologies, IV) Neutron Generation Target Technologies, V) Automatic Control System Technologies, and VI) Exemplary Applications and Indications. Certain technologies within and between each group may be used in combination.

Individually or collectively, these techniques may be applied to any high energy ion beam generator system having associated components. To illustrate embodiments of the techniques, many of the features are described in the context of a high energy ion beam generator employed by Phoenix Nuclear Labs, LLC (Monona, Wisconsin). See, for example, U.S. Patent Publication Nos. 2011/0096887, 2012/0300890, and 2016/0163495, as well as U.S. Patent Nos. 8,837,662, and 9,024,261, which are incorporated herein by reference in their entirety. However, these technologies are not available from Pantechnik (Bayeux, France), D-Pace (British Columbia, Canada), Adelphi Tech Inc. It should be understood that the present invention may be applied to a wide range of high energy ion beam generators and their component parts, including those from Starfire Industries, LLC (Rosewood City, California) (see, e.g., U.S. Patent Publication No. 2014/0179978, which is incorporated herein by reference in its entirety), Starfire Industries, LLC (Champaign, Illinois) (see, e.g., U.S. Patent No. 9,008,256, which is incorporated herein by reference in its entirety), Thermo Fisher Scientific (see, e.g., U.S. Patent No. 8,384,018, which is incorporated herein by reference in its entirety), and Sodern (Limeil-Brevannes, France).

Applications of such systems include, but are not limited to, semiconductor manufacturing (e.g., silicon fracturing for photovoltaic semiconductor applications), isotope production and separation, cyclotron injection systems, accelerator mass spectrometry, security (e.g., explosives detection), industrial diagnostics and quality control, and imaging. Cyclotrons are widely used across medical and industrial sectors. Ion beams are used in a wide range of settings in the semiconductor industry. Better ion sources translate into cheaper, more efficient, and more effective production techniques for circuit components, the building blocks of all modern IC-based technology. In another example, negative ion sources find application in the field of magnetic confinement fusion energy.

For decades, scientists have been trying to develop energy sources based on nuclear fusion reactions because they could potentially provide essentially limitless amounts of clean energy with virtually harmless by-products. Although fusion energy technology has made great strides over the past few decades, there are still several technical challenges that have hindered the development of clean fusion energy reactors. One challenge faced by fusion energy is unreliable high current negative ion sources. Existing negative ion fusion injectors use filaments and/or magnetically coupled plasmas, which suffer from many of the deficiencies discussed herein. A reliable, long-life negative ion source would significantly increase ion source conversion efficiency, lifetime, reliability, and current output.

In some embodiments, provided herein is a device comprising: a) a waveguide comprising: i) a proximal end having an electromagnetic wave entry point; ii) a distal end having an electromagnetic wave exit point; and iii) an outer wall extending between the proximal and distal ends and configured to propagate electromagnetic waves; and b) an inverse impedance matching component located inside the waveguide component, the inverse impedance matching component extending from the distal end of the waveguide at least part way toward the proximal end of the waveguide, the inverse impedance matching component having a distal end and a proximal end, the distal end of the impedance matching component being located at or near the distal end of the waveguide and having a larger cross-sectional area than the proximal end of the inverse impedance matching component.

In some embodiments, the reverse impedance matching component is made of metal. In further embodiments, the reverse impedance matching component is configured to be cooled by water. In other embodiments, the reverse impedance matching component is located along a centerline of the waveguide. In additional embodiments, the reverse impedance matching component is supported by one or more support legs attached to an outer wall of the waveguide. In some embodiments, the electromagnetic waves are microwaves. In further embodiments, the cross-sectional area of the reverse impedance matching component at the distal end is at least two, three, or four times larger than the cross-sectional area of the reverse impedance matching component at the proximal end. In some embodiments, the reverse impedance matching component includes one or more steps (e.g., 2, 3, 4, 5, 6, 7...10...or 20) that allow the cross-sectional area to vary from the proximal end to the distal end of the reverse impedance matching component.

In further embodiments, the anti-impedance matching component includes a taper from the proximal end to the distal end of the anti-impedance matching component, thereby allowing the cross-sectional area to vary. In some embodiments, the cross-sectional area at the distal end of the anti-impedance matching component is large enough to block all or nearly all backflowing electrons when the device is part of an accelerator system.

In certain embodiments, a system is provided herein that includes: a) an electromagnetic wave source; b) a plasma chamber; and c) a device as described above (and herein) consisting of a waveguide and an inverse impedance matching component. In some embodiments, a proximal end of the waveguide is operably attached to the electromagnetic wave source and a distal end of the waveguide is operably attached to the plasma chamber. In further embodiments, the electromagnetic wave source includes a microwave source.

In some embodiments, a system includes: a) a computer processor; b) a non-transient computer memory having one or more computer programs and a database, the one or more computer programs comprising accelerator system monitoring and/or optimization software; and c) an accelerator system that generates a high energy ion beam (e.g., generates neutrons or protons), in operative communication with the non-transient computer memory and capable of being automatically adjusted by the accelerator system monitoring and/or optimization software, the system including one or more of the following subsystems: i) an ion source and ion source monitoring components; and ii) a focusing solenoid magnet and focusing solenoid magnet monitoring components. A system is provided herein that includes an accelerator system that includes: iii) a tube opening and a tube opening monitoring component; iv) a solid or gas target and a solid or gas target monitoring component; v) an ion beam extraction and secondary electron suppression component and an extraction and suppression monitoring component; vi) a beam generation subsystem and a beam generation subsystem monitoring component; vii) a beam focusing and steering subsystem and a beam focusing and steering subsystem monitoring component; viii) an accelerator/resistor subsystem and an accelerator/resistor subsystem monitoring component; ix) a beam steering subsystem and a beam steering subsystem monitoring component; and x) a pressurized gas subsystem component and a pressurized gas subsystem component monitoring component.

In some embodiments, 1) the ion source monitoring components include mass flow meters, thermocouples, coolant flow meters, and/or pressure gauges; 2) the focusing solenoid monitoring components include thermocouples, coolant flow meters, voltage monitors, and/or current monitors; 3) the tube opening monitoring components include cameras, thermocouples, and/or coolant flow meters; 4) the solid or gas target monitoring components include cameras, thermocouples, coolant flow meters, and/or radiation detectors; 5) the extraction and suppression monitoring components include pressure gauges, thermocouples, current monitors, and/or voltage monitors; 6) the beam generation subsystem monitoring components include current monitors and/or emittance scanners; and 7) the pressurized gas subsystem component monitoring components include pressure gauges and/or gas analyzers.

In certain embodiments, the accelerator system monitoring and/or optimization software is configured to collect and analyze multiple different settings for the subsystems and calculate optimized settings for such subsystems. In other embodiments, the accelerator system monitoring and/or optimization software is configured to change settings in one or more of the subsystems to at least partially optimize the performance of the accelerator system.

In some embodiments, the ion source plasma chamber includes: a) an ion source plasma chamber having a source axis along a direction of a beam exiting the plasma chamber; b) at least one ion source magnet (e.g., a solenoid or permanent magnet), the at least one ion source magnet having an opening and at least one outer wall, the at least one ion source plasma chamber extending through the opening of the at least one ion source magnet; c) at least one receiving component attached to or integral with the at least one outer wall of the at least one ion source magnet; and d) a ferromagnetic enclosure, the at least one ion source magnet having a source axis extending through the opening of the at least one ion source magnet. The magnet and ion source plasma chamber are inside a ferromagnetic enclosure, and at least one ion source magnet can be moved to a plurality of different positions inside the ferromagnetic enclosure along a source axis of the plasma chamber, and the ferromagnetic enclosure has at least one longitudinal opening extending along the direction of the source axis and aligned with the receiving component, and e) at least one adjustment component extending through the longitudinal opening and configured to attach to the receiving component, and capable of fixing the at least one ion source magnet at a plurality of different positions inside the ferromagnetic enclosure. A system is provided herein.

In certain embodiments, the receiving component comprises a threaded metal connector, or a snap receiver, or a pinhole. In certain embodiments, the adjustment component comprises a threaded bolt. In other embodiments, the receiving component is glued to the at least one ion source magnet (e.g., a solenoid magnet or a permanent magnet). In some embodiments, the at least one ion source magnet is at least partially encapsulated in epoxy. In other embodiments, the at least one ion source magnet comprises two, or three, or four ion source magnets. In additional embodiments, the at least one longitudinal opening comprises at least two, three, or four longitudinal openings.

In some embodiments, a method is provided herein that includes a) providing a system as described immediately above or elsewhere herein; b) moving at least one ion source magnet (e.g., a solenoid magnet or a permanent magnet) from a first position among the plurality of positions to a second position among the plurality of positions; c) inserting at least one adjustment component into the at least one receiving component through the at least one longitudinal opening; and d) securing the at least one adjustment component to the at least one receiving component, thereby securing the at least one ion source magnet at the second position. In some embodiments, the at least one ion source magnet comprises a first and a second ion source magnet, and both the first and second ion source magnets are moved from the first position to the second position and secured at the second position.

In some embodiments, provided herein is an article of manufacture comprising a metal assembly of an accelerator system that generates a high energy ion beam, the metal assembly partially intercepting the high energy ion beam when positioned in the accelerator system, the metal assembly comprising a first metal component, a second metal component, and a filler metal, the filler metal attaching the first metal component to the second metal component at a joint (e.g., a brazed joint).

In an embodiment, provided herein is an article of manufacture comprising a metal assembly of an accelerator system that generates a high energy ion beam, the metal assembly, when positioned in the accelerator system, i) partially intercepts the high energy ion beam and ii) is in a vacuum environment, the metal assembly comprising i) at least one water cooling channel and ii) a first metal component, a second metal component, and a filler metal, the filler metal attaching the first metal component to the second metal component at a joint (e.g., a brazed joint).

In certain embodiments, the first and second metal components are comprised of highly thermally conductive metals (e.g., copper, aluminum, etc.). In some embodiments, the filler metal has a lower melting point than the first and second metal components. In certain embodiments, the first metal component comprises a tube sheet and the second metal component comprises a plate plug. In certain embodiments, the filler metal comprises BNi-7 alloy, BNi-6 alloy, Pd ₁₀₀ , Pt ₁₀₀ , Ni ₁₀₀ , or other metal or alloy suitable for brazing the first and second metal components together. In some embodiments, the first metal component comprises a first item selected from the group consisting of a first tube, a tube cap, a different tube sheet, and a valve, and the second metal component comprises a second item selected from the group consisting of a second tube, a tube cap, a different tube sheet, and a valve. In some embodiments, the at least one water cooling channel comprises at least two water cooling channels (eg, 2, 3, 4, 5, 6...10...or 25 water cooling channels).

In additional embodiments, provided herein is a system comprising: a) an accelerator system generating an ion beam (e.g., a high-energy ion beam); and b) a metal assembly positioned within the accelerator system such that the metal assembly i) partially intercepts the high-energy ion beam and ii) is within a vacuum environment, the metal assembly comprising a first metal component, a second metal component, and a filler metal, the filler metal attaching the first metal component to the second metal component at a joint (e.g., a brazed joint).

In some embodiments, a system is provided herein that includes: a) an accelerator system that generates an ion beam (e.g., a high-energy ion beam); and b) a metal assembly, the metal assembly positioned within the accelerator system such that the metal assembly i) partially intercepts the high-energy ion beam and ii) is within a vacuum environment, the metal assembly including i) at least one water-cooled channel; and ii) a first metal component, a second metal component, and a filler metal, the filler metal attaching the first metal component to the second metal component at a joint (e.g., a brazed joint).

In one embodiment, a method is provided herein that includes: a) attaching a first metal component to a second metal component with a filler metal using a brazing technique to produce a metal assembly; and b) inserting the metal assembly into an accelerator system that generates a high-energy ion beam, the metal assembly being positioned to partially intercept the high-energy ion beam.

In some embodiments, the metal assembly further comprises at least one water cooling channel. In other embodiments, the metal assembly is further positioned such that it is within a vacuum environment.

In some embodiments, a system is provided herein that includes a) a high voltage dome; b) an ion source plasma chamber located inside the high voltage dome; c) an extraction component operably coupled to the ion source plasma chamber; and d) a gas removal subsystem that includes: i) an exhaust component located inside the high voltage dome; ii) an insulating hose, a first portion of the insulating hose located inside the high voltage dome and a second portion of the insulating hose located outside the high voltage dome in an area of lower voltage; iii) a first vacuum pump located inside the high voltage dome and operably coupled to the exhaust component and the extraction component, configured to remove gas from the extraction component and deliver the gas to the exhaust component; and iv) a second vacuum pump located inside the high voltage dome and operably coupled to the exhaust component, configured to receive gas from the exhaust component at a first pressure and deliver gas to the insulating hose at a second pressure, the second pressure being higher than the first pressure.

In some embodiments, the system further comprises e) an outer pressure vessel, wherein at least a portion of the high voltage dome, the ion source plasma chamber, the extraction component, the exhaust component, the first vacuum pump, the second pump, and the insulating hose are located within the pressure vessel. In other embodiments, the insulating hose is configured to vent the gas to the atmosphere. In some embodiments, the gas is a non-ionized gas. In other embodiments, the non-ionized gas is deuterium gas. In some embodiments, the system further comprises a gas. In certain embodiments, the gas is a non-ionized gas. In additional embodiments, the insulating hose has a helical shape. In further embodiments, the insulating hose has about 20-30 helical turns and is about 5-15 feet long. In other embodiments, the first vacuum pump comprises a pump selected from a turbomolecular pump, a cryopump, an ion pump, and a high vacuum pump. In some embodiments, the second vacuum pump comprises a roughing pump. In another embodiment, the system further comprises e) an inner pressure vessel located inside the high voltage dome, the second vacuum pump is located in the inner pressure vessel, and the following components are not located in the pump pressure vessel: the high voltage dome, the ion source plasma chamber, the extraction component, and the first vacuum pump.

In some embodiments, a gas removal subsystem configured to be introduced into a high energy ion beam generating system having a high voltage dome and an extraction component is provided herein, the gas removal subsystem comprising: a) an exhaust component configured to be positioned inside the high voltage dome; b) an insulating hose, a first portion of the insulating hose configured to extend through an opening in the high voltage dome; c) a first vacuum pump configured to be positioned inside the high voltage dome and operably coupled to the exhaust component and the extraction component, the first vacuum pump configured to remove gas from the extraction component and deliver the gas to the exhaust component; and d) a second vacuum pump configured to be positioned inside the high voltage dome and operably coupled to the exhaust component, the second vacuum pump configured to receive gas from the exhaust component at a first pressure and deliver gas to the insulating hose at a second pressure, the second pressure being higher than the first pressure.

In certain embodiments, a method is provided herein that includes: a) providing a system as described above or otherwise herein; and b) activating a gas removal subsystem such that gas present in the extraction component is i) removed by a first vacuum pump to an exhaust component, ii) received by a second vacuum pump from the exhaust component at a first pressure and delivered to an insulated hose at a second pressure higher than the first pressure, and iii) delivered by the insulated hose to atmosphere. In some embodiments, the gas in the extraction component is a non-ionized gas that has traveled from an ion source plasma chamber to the extraction component.

In some embodiments, a system is provided herein that includes: a) an outer pressure vessel; b) an inner pressure vessel located inside the outer pressure vessel; c) an exhaust component located inside the outer pressure vessel, where a portion of the exhaust component is also located within the inner pressure vessel; d) an insulating hose located inside the outer pressure vessel, where a portion of the insulating hose is also located within the inner pressure vessel; e) a first vacuum pump located inside the outer pressure vessel and operably connected to the exhaust component; and f) a second vacuum pump located inside the inner pressure vessel and operably connected to the exhaust component.

In certain embodiments, the outer pressure vessel comprises a gas at a higher pressure than the gas in the inner pressure vessel. In some embodiments, the gas in the inner pressure vessel is at about atmospheric pressure. In further embodiments, the first vacuum pump is configured to be operably coupled to an extraction component of an accelerator system that generates a high energy ion beam, the first vacuum pump configured to remove gas from the extraction component and deliver the gas to an exhaust component. In additional embodiments, the second vacuum pump is configured to receive gas from the exhaust component at a first pressure and deliver the gas to an insulated hose at a second pressure, the second pressure being higher than the first pressure. In certain embodiments, the system further comprises an extraction component. In further embodiments, the system further comprises an ion source plasma chamber located inside the outer pressure vessel. In some embodiments, the extraction component is operably coupled to the ion source plasma chamber.

In some embodiments, a system is provided herein that includes: a) at least one high voltage component held at a high voltage in an accelerator system that generates a high energy ion beam; and b) a power component electrically coupled (and/or mechanically coupled) to the at least one high voltage component, the power component providing power to the at least one high voltage component (e.g., in a manner that is electrically isolated from ground), the power component including a V-belt, the V-belt including a plurality of sections (e.g., 3...25...100...400 sections), and which is i) a poor electrical conductor or ii) a non-electrical conductor.

In further embodiments, the V-belt is comprised of a polyester polyurethane composite. In some embodiments, the power component further comprises a motor and a generator. In additional embodiments, the power component further comprises a first V-belt pulley operably attached to the motor and a second V-belt pulley operably attached to the generator. In some embodiments, at least one high voltage component comprises an ion source plasma chamber.

In some embodiments, a) an accelerator subsystem for generating a high energy ion beam includes: i) an ion source plasma chamber; ii) a microwave generating component for generating microwaves; iii) a power source operably coupled to the microwave generating component; iv) a waveguide positioned to receive the microwaves and deliver them to the ion source plasma chamber, the waveguide generating an ion source when the microwaves contact a gas in the ion plasma chamber; v) an ion beam extraction component operably coupled to the ion source plasma chamber for extracting a low energy ion beam from the ion plasma chamber; and iv) an accelerator. Provided herein is a system comprising: an accelerator subsystem comprising a column, an accelerator component comprising an accelerator entrance aperture for receiving a low-energy ion beam, and an accelerator exit aperture for delivering a high-energy ion beam; and b) a power modulation component operably coupled to a power source, the power modulation component configured to modulate the power flowing from the power source to the microwave generation component such that microwaves incident on the waveguide are rapidly pulsed and/or extinguished/generated, thereby rapidly pulsing and/or extinguishing/generating the high-energy ion beam. In an embodiment, the accelerator system is a direct injection accelerator system. In another embodiment, the microwave generation component comprises a magnetron.

In certain embodiments, methods are provided herein that include a) providing a system as described above (and herein); and b) activating accelerator subsystems and power modulation components such that a high energy ion beam is generated, the high energy ion beam is rapidly pulsed, and/or extinguished/generated.

In some embodiments, a method is provided herein that includes: a) positioning an ion beam generating component in a direct injection accelerator system that generates a high energy ion beam at a first distance from an accelerator inlet of an accelerator column; and b) positioning the ion beam generating component at a second distance from the inlet of the accelerator column, the second distance being different from the first distance, the second distance improving performance of the direct injection accelerator system. In some embodiments, the first and second distances are within a range of 10-500 mm.

In some embodiments, a) a direct injection accelerator subsystem for generating a high energy ion beam, the accelerator system comprising: i) an ion source plasma chamber; ii) a microwave generating component for generating microwaves; iii) a power source operably coupled to the microwave generating component; iv) a waveguide positioned to receive the microwaves and deliver them to the ion source plasma chamber, where an ion beam is generated when the microwaves contact gas in the ion plasma chamber; v) an extraction component operably coupled to the ion source plasma chamber; and iv) an accelerator component comprising an accelerator column and an accelerator inlet opening for receiving the ion beam; and b) a vacuum component operably coupled to the extraction component and/or the accelerator component, the vacuum component configured to reduce pressure in the extraction component and/or the accelerator component. In certain embodiments, the reduction in pressure is at a level that reduces the diameter of the high energy ion beam.

In some embodiments, methods are provided herein that include a) providing a system as described above (and herein); and b) activating a direct implant accelerator subsystem and vacuum components such that a high-energy ion beam is generated such that the high-energy ion beam has a smaller diameter than the high-energy ion beam would have in the absence of the pressure reduction.

In some embodiments, a system is provided herein that includes: a) an accelerator subsystem for generating a high energy ion beam, the accelerator system including: i) a high voltage dome; ii) an ion beam generating component located inside the high voltage dome; and iii) an accelerator component including an accelerator column; and b) a water resistor subsystem including: i) a water circulation component including a water piping and a water reservoir; and ii) a water resistor element extending along the accelerator column, the water resistor element including non-conductive and/or insulating tubing fluidly coupled to or integral with the water piping such that controlled conductivity water circulation in the water circulation component passes through the water resistor element.

In some embodiments, the system further comprises a controlled conductivity water, the controlled conductivity water being comprised of i) deionized water, and 2) deionized (DI) resin, and a metal salt. In further embodiments, the accelerator component further comprises a plurality of grading rings extending along the accelerator column. In additional embodiments, the insulating tubing is comprised of a material selected from the group consisting of polycarbonate, polymethyl methacrylate (PMMA), and polyethylene. In further embodiments, the water circulation component further comprises a water pump, a heat exchanger, and/or a DI resin source component. In some embodiments, the controlled conductivity water includes a sufficient amount of DI resin such that the deionized water has a resistivity of 15 megaohm-cm or greater. In further embodiments, the metal salt is selected from the group consisting of copper sulfate, sodium chloride, ammonium chloride, magnesium sulfate, and sodium thiosulfate. In further embodiments, the water resistor element is capable of withstanding a voltage of up to about 300 kV DC and removing up to about 3 kW, or up to about 5 kW of heat.

In certain embodiments, a method is provided herein that includes a) providing a system as described above (and described herein); and b) activating the accelerator subsystem and the water resistor subsystem such that, while a high energy ion beam is being generated, controlled conductivity water circulates through the water circulation components and the water resistor elements act as electrical resistors along the accelerator column.

In another embodiment, a system is provided herein that includes: a) at least one high voltage power supply (HVPS) configured to deliver power to components of an accelerator subsystem that generate a high energy ion beam; and b) a water resistor subsystem that includes: i) a water circulation component that includes a water piping and a water reservoir; and ii) a water resistor element that includes non-conductive and/or insulating tubing fluidly coupled to or integral with the water piping such that controlled conductivity water circulation in the water circulation component passes through the water resistor element.

In certain embodiments, a method is provided herein that includes a) providing a system as described above (and as described herein) and b) testing at least one HVPS using a water resistor subsystem as a test load.

In some embodiments, a method for designing lenses is provided herein that includes: a) inputting the following parameters at a plasma lens aperture of an accelerator system into a software application: beam current, extraction voltage, ion species ratio, maximum electric field, and ion current density; b) receiving output from the software for designing at least one lens in an electrostatic lens stack, the electrostatic lens stack comprising a plasma lens, an extraction lens, a suppression lens, and an exit lens; and c) fabricating the at least one lens based on the output. In an embodiment, the software application comprises a PBGUNS software application. In a further embodiment, the at least one lens comprises at least two, at least three, or all four of the lenses in the electrostatic lens stack. In a further embodiment, the method further includes inputting at least one of the following into the software application: grid precision, empirically determined beam neutralization factor, and electron and ion temperatures in the source plasma.

In some embodiments, provided herein is a system (e.g., for use in or part of a high energy ion beam generator system) that includes an extraction lens stack having a) a plurality of insulating balls (e.g., alumina ceramic, aluminum nitride, sapphire, diamond, or other oxide or non-oxide ceramic balls) positioned between the lens gaps of the extraction lens stack. In some embodiments, a minimum of three insulating balls are positioned between each lens gap. In some embodiments, the three insulating balls are evenly spaced in azimuth coordinates. In some embodiments, the lens stack is held together using metal bolts. Additionally, provided herein is a method of generating neutrons and protons using such a system to provide, for example, enhanced mechanical stability, beam quality, and protection of source and beamline components while increasing the total current that can be reliably transported to the target.

In some embodiments, provided herein is a system (e.g., for use in, or part of, a neutron generator system) that includes a) a high power density solid target comprised of a reactive species (e.g., a reactive hydrogen species such as deuterium or tritium) embedded in a solid matrix, and b) a cooling component. The solid matrix may be made of any desired material, including, but not limited to, titanium.

In some embodiments, the cooling component is a closed loop component. In some embodiments, the coolant flow path is integrated into the solid target. In some embodiments, the system further comprises a coolant source providing a coolant to be flowed through the cooling component. In some embodiments, the coolant is selected from the group consisting of water, glycol (e.g., (poly)ethylene glycol), oil, helium, or the like. In some embodiments, the closed loop component comprises a deionization subcomponent for deionizing the coolant flowing therethrough. In some embodiments, the closed loop component comprises a filtration subcomponent for filtering the coolant flowing therethrough. In some embodiments, the coolant component comprises a cooling device positioned to pre-cool the coolant prior to contact with the target.

In some embodiments, the target is manufactured with thin walls to maximize the effect of the coolant. In some embodiments, the walls have a thickness of 0.02 inches or less (e.g., 0.01 inches). In some embodiments, the walls are made of a material selected from the group consisting of copper, silver, gold, diamond, diamond-like carbon, or combinations thereof.

In some embodiments, the target includes a passage with a spiral to increase surface area relative to a target lacking a spiral. In some embodiments, the spiral is a fin, or a rib, or a combination thereof.

In some embodiments, the cooling component is configured for laminar flow of coolant. In some embodiments, the cooling component includes channels with irregular surface features (e.g., dimples, helical indentations, or combinations thereof). In some embodiments, the coolant component is configured for laminar flow of coolant with channels with irregular surface features (e.g., dimples, helical indentations, or combinations thereof).

Methods employing such systems are also provided. For example, in some embodiments, a method for generating neutrons using a high power density solid target is provided by using any of the above systems. In some embodiments, the method involves depositing the energy of an ion beam into a small volume.

In some embodiments, provided herein is a system (e.g., for use in, or part of, a neutron generator system) comprising: a) a solid target; b) a vacuum system; and c) a noble gas source in fluid communication with the vacuum system and configured to emit a noble gas in the vicinity of the solid target. In some embodiments, the noble gas is argon. Further provided herein is a method of purifying a neutron generator solid target, comprising exposing the solid target to a noble gas (e.g., while the solid target is exposed to an ion beam). In some embodiments, the noble gas is flowed at 1-10 cubic centimeters per minute.

In some embodiments, a system (e.g., for use in or part of a neutron generator system) is provided herein that includes: a) an accelerator that generates an ion beam; b) a target (e.g., a gas target) positioned to be contacted by the ion beam; c) a target aperture that separates the accelerator and the target; d) a steering component that focuses the ion beam into the aperture; and e) a plurality of thermal sensors positioned near an upstream-facing surface of the target aperture. In some embodiments, the plurality of thermal sensors includes four thermal sensors equally spaced at 90 degree intervals around the axis of the aperture. In some embodiments, the thermal sensor includes a thermocouple (e.g., a copper-constantan thermocouple). In some embodiments, the thermal sensor is a platinum resistance temperature detector (RTD), a thermistor, or a semiconductor temperature sensor.

In some embodiments, the system further includes a processor that receives the temperature signals from the sensors. In some embodiments, the processor sums the temperature signals from the sensors to generate an average target aperture temperature. In some embodiments, the processor adjusts the ion beam position based on the average target aperture temperature to minimize the temperature of the target aperture.

Further provided herein is a method of steering an ion beam to a target aperture in a neutron generator system, the method including: a) measuring temperature at multiple locations around the target aperture; and b) steering the position of the ion beam (e.g., using the system described above) to minimize the temperature at the target aperture.

In some embodiments, provided herein is a system (e.g., for use in or part of a neutron generator system) comprising: a) an accelerator generating an ion beam; b) a target (e.g., a gas target) positioned to be contacted by the ion beam; c) a target aperture separating the accelerator and the gas target; and d) a reverse gas jet that increases a pressure differential across the aperture. In some embodiments, the reverse gas jet comprises a constriction gap, a nozzle having a nozzle angle and a nozzle length, and a plenum. In some embodiments, the reverse gas jet comprises a nozzle that diverges after it converges. In some embodiments, the reverse gas jet comprises a nozzle aperture of about 3/8 inch. In some embodiments, the reverse gas jet comprises a constriction gap of less than 0.01 inch. In some embodiments, the reverse gas jet comprises a nozzle angle of 12.5 degrees. Further provided herein is a method of increasing a pressure differential across a target aperture of a neutron generator, comprising employing a reverse gas jet at the target aperture.

In some embodiments, provided herein is a system (e.g., for use in or part of a neutron generator system) that includes a beam scraper, the beam scraper movable into the path of the ion beam using a motor, the motor mounted to a generator system outside of a vacuum vessel containing the target. In some embodiments, the motor is connected to the beam scraper via a magnetically coupled vacuum feedthrough (e.g., a linear motion feedthrough). In some embodiments, the motor, beam scraper, and connections therebetween are all-metal with brazing fabrication. Further provided herein is a method of blocking a portion of an ion beam striking a target in a neutron generator, the method including moving a beam scraper into a position contacted by the ion beam using a motor mounted to a generator system outside of a vacuum vessel containing the target.

In some embodiments, a system is provided herein that includes a) a high energy ion beam generator device having a first interlock, and b) a user control station having a second interlock, the high energy ion beam generator and the user control station being connected via a fiber optic interlock that includes a number of normally closed switches in a series loop that remain closed to indicate that the generator is safe to operate, a number of normally open switches in a parallel loop that remain open to indicate that the generator is safe to operate, or both the series and parallel loops. In some embodiments, the high energy ion beam generator and the user control station are electrically isolated from each other. In some embodiments, the fiber optic interlock includes a frequency generator. In some embodiments, the frequency generator triggers a fiber optic transmitter that pulses light at a set frequency. In some embodiments, the system is configurable between a number of distinctly different frequencies, for example for the purpose of having multiple channels with no interoperability between the channels to prevent erroneous cross connections. In some embodiments, the system includes control software that manages the fiber optic interlock. In some embodiments, the control software operates a multiple signal verification procedure of the fiber optic interlock. Methods of using such systems are also provided. In some embodiments, the method includes transmitting information via a fiber optic interlock to and from the high energy ion beam generator and the user control station.

In some embodiments, a system (e.g., for use in or part of a high energy ion beam system) is provided herein that includes: a) a high energy ion beam generator device that generates a beam; and b) a damage mitigation component that includes: i) a plurality of sensors positioned on the device and configured to monitor a plurality of regions of the device that may interact with the beam; and ii) control software configured to communicate with the plurality of sensors, generate an alert or alarm, and adjust the device in response to the alert or alarm. In some embodiments, one or more of the sensors measure a temperature of a region of the device. In some embodiments, one or more of the sensors measure a coolant (e.g., water) flow rate. In some embodiments, one or more of the sensors are in a continuous sensing mode. In some embodiments, one or more or all of the sensors have a threshold associated therewith that generates an alert or alarm if exceeded. In some embodiments, the alert comprises a user warning. In some embodiments, the alarm triggers a device shutdown or reset. In some embodiments, the alarm is a latch arm that requires the user to reset the device prior to further operation. In some embodiments, the control software filters out background EMI. In some embodiments, the filtered out background EMI is below a predetermined threshold duration or frequency so as to distinguish it from a potentially harmful event. A method of using the system is also provided. In some embodiments, the method includes using the system to detect a potentially damaging event. In some embodiments, the method includes generating an alert or alarm and a desired associated response (e.g., a warning, an automatic system shutdown, etc.).

In some embodiments, provided herein is a system (e.g., for use in or part of a high energy ion beam system) comprising: a) a high energy ion beam generator device; and b) an arc down mitigation component comprising: i) a plurality of sensors positioned on the device and configured to monitor conditions consistent with an arc down event; and ii) control software configured to communicate with the plurality of sensors, generate an alert or alarm, and adjust the device in response to the alert or alarm. In some embodiments, the alarm triggers an automatic recovery sequence that returns the device to normal operation without user intervention. Methods of using the system are also provided. In some embodiments, the method includes using the system to respond to an arc shutdown event.

In some embodiments, provided herein is a high energy ion beam generator system that includes closed loop control components that manage high voltage power supply (HVPS) setpoints. In some embodiments, the components also control one or more other system functions, including, but not limited to, microwave power, focusing, and steering. In some embodiments, provided herein is a method of controlling high energy ion flux output variability in a high energy ion beam generator that includes managing high voltage power supply (HVPS) setpoints with closed loop control components.

In some embodiments, provided herein is a neutron guidance system for use in neutron radiography comprising a collimator comprising a high density polyethylene (HDPE) layer, a borated polyethylene layer, a metal layer (e.g., comprising an aluminum and/or lead layer), and a cadmium layer.

In some embodiments, provided herein is a system for neutron radiography comprising one or more or all of: a) a neutron source (e.g., a _2.45 MeV neutron source), b) a high density polyethylene (HDPE) layer, a borated polyethylene layer, a metal layer (e.g., comprising an aluminum and/or lead layer), and a cadmium layer, c) a detector, d) a moderator (e.g., a graphite moderator and/or aD2O moderator), and e) an underground shield (e.g., comprising an earth, concrete, or other protective layer). In some embodiments, the system comprises an offset collimator that is not directly aligned with the fast neutron source.

Further provided herein is a method of imaging a sample, comprising exposing the sample to neutrons generated by the above method.

In some embodiments, systems and methods for semiconductor manufacturing are provided herein. In some embodiments, the system comprises an accelerator system that generates a high energy ion beam (e.g., a hydrogen ion beam) as described herein, which directs the beam at a component that holds the semiconductor material. In some embodiments, the method comprises contacting the semiconductor material with protons generated from a high energy ion beam generator system as described herein. In some embodiments, the method further comprises creating a thin film wafer by fracturing the semiconductor material (e.g., at a fracturing site formed by the implanted hydrogen ions). In some embodiments, the method further comprises fabricating a photovoltaic (PV) wafer from the thin film wafer. In some embodiments, the method further comprises fabricating a solar panel comprising the photovoltaic wafer. In some embodiments, the method further comprises fabricating a light emitting diode (LED) comprising the photovoltaic wafer. In some embodiments, the method further comprises fabricating a light emitting diode (LED) from the thin film wafer.
The present specification also provides, for example, the following items:
(Item 1)
A device, the device comprising:
a) a waveguide, said waveguide comprising:
i) a proximal end having an electromagnetic wave entry point;
ii) a distal end having an electromagnetic wave exit point;
iii) an outer wall extending between the proximal end and the distal end and configured to propagate electromagnetic waves; and
b) an inverse impedance matching component located inside the waveguide component;
the inverse impedance matching component extends from the distal end of the waveguide at least part way toward the proximal end of the waveguide;
A device, wherein the inverse impedance matching component has a distal end and a proximal end, the distal end of the impedance matching component being located at or near the distal end of the waveguide and having a larger cross-sectional area than the proximal end of the inverse impedance matching component.
(Item 2)
3. The device of claim 1, wherein the inverse impedance matching component comprises a metal.
2. The device of claim 1, wherein the inverse impedance matching component is configured to be cooled by water.
(Item 4)
2. The device of claim 1, wherein the inverse impedance matching component is located along a centerline of the waveguide.
(Item 5)
5. The device of claim 4, wherein the inverse impedance matching component is supported by one or more support legs attached to an outer wall of the waveguide.
(Item 6)
2. The device of claim 1, wherein the electromagnetic waves are microwaves.
(Item 7)
2. The device of claim 1, wherein a cross-sectional area of the anti-impedance matching component at the distal end is at least two, three, or four times larger than a cross-sectional area of the anti-impedance matching component at the proximal end.
(Item 8)
2. The device of claim 1, wherein the reverse impedance matching component comprises one or more steps that allow the cross-sectional area to vary from the proximal end to the distal end of the reverse impedance matching component.
(Item 9)
2. The device of claim 1, wherein the reverse impedance matching component comprises a taper from the proximal end to the distal end of the reverse impedance matching component, thereby allowing the cross-sectional area to vary.
(Item 10)
2. The device of claim 1, wherein the cross-sectional area of the inverse impedance matching component at the distal end is large enough to block all or nearly all backflowing electrons when the device is part of an accelerator system.
(Item 11)
a) an electromagnetic wave source;
b) a plasma chamber; and
c) A system comprising the device according to claim 1.
(Item 12)
12. The system of claim 11, wherein the proximal end of the waveguide is operably attached to the electromagnetic wave source and the distal end of the waveguide is operably attached to the plasma chamber.
(Item 13)
12. The system of claim 11, wherein the electromagnetic wave source comprises a microwave source.
(Item 14)
1. A system comprising:
a) a computer processor;
b) a non-transitory computer memory comprising one or more computer programs and a database, the one or more computer programs comprising accelerator system monitoring and/or optimization software; and
c) an accelerator system for generating a high energy ion beam;
The accelerator system includes the following subsystems in operative communication with the non-transitory computer memory and capable of being automatically adjusted by the accelerator system monitoring and/or optimization software:
i) an ion source and an ion source monitoring component;
ii) a focusing solenoid magnet and a focusing solenoid magnet monitoring component;
iii) tube opening and tube opening monitoring components;
iv) a solid or gas target and a solid or gas target monitoring component;
v) an extraction and suppression component and an extraction and suppression monitoring component;
vi) a beam generation subsystem and a beam generation subsystem monitoring component;
vii) a beam focusing and steering subsystem and a beam focusing and steering subsystem monitoring component;
viii) an accelerator/resistor subsystem and an accelerator/resistor subsystem monitoring component;
ix) a beam-steering subsystem and a beam-steering subsystem monitoring component;
x) a pressurized gas subsystem component and a pressurized gas subsystem component monitoring component.
(Item 15)
15. The system of claim 14, wherein: 1) the ion source monitoring components comprise mass flow meters, thermocouples, coolant flow meters, and/or pressure gauges; 2) the focusing solenoid monitoring components comprise thermocouples, coolant flow meters, voltage monitors, and/or current monitors; 3) the tube opening monitoring components comprise cameras, thermocouples, and/or coolant flow meters; 4) the solid or gas target monitoring components comprise cameras, thermocouples, coolant flow meters, and/or radiation detectors; 5) the extraction and suppression monitoring components comprise pressure gauges, thermocouples, current monitors, and/or voltage monitors; 6) the beam generation subsystem monitoring components comprise current monitors and/or emittance scanners; and 7) the pressurized gas subsystem component monitoring components comprise pressure gauges and/or gas analyzers.
(Item 16)
15. The system of claim 14, wherein the accelerator system monitoring and/or optimization software is configured to collect and analyze a plurality of different settings of the subsystems and calculate optimized settings for such subsystems.
(Item 17)
17. The system of claim 16, wherein the accelerator system monitoring and/or optimization software is configured to modify the settings in one or more of the subsystems to at least partially optimize performance of the accelerator system.
(Item 18)
1. A system comprising:
a) an ion source plasma chamber having a source axis along a direction of a beam exiting the plasma chamber;
b) at least one ion source magnet, the at least one ion source magnet comprising an opening and at least one outer wall, the ion source plasma chamber extending through the opening of the at least one ion source magnet;
c) at least one receiving component attached to or integral with said at least one outer wall of said at least one ion source magnet;
d) a ferromagnetic enclosure, wherein the at least one ion source magnet and the ion source plasma chamber are inside the ferromagnetic enclosure, the at least one ion source magnet can be moved to a plurality of different positions inside the ferromagnetic enclosure along the source axis of the plasma chamber, and the ferromagnetic enclosure has at least one longitudinal opening extending along the direction of the source axis and aligned with the receiving component;
e) at least one adjustment component extending through said longitudinal opening and configured to attach to said receiving component;
the at least one adjustment component is capable of fixing the at least one ion source magnet at the plurality of different positions inside the ferromagnetic enclosure.
system.
(Item 19)
20. The system of claim 18, wherein the receiving component comprises a threaded metal connector.
(Item 20)
20. The system of claim 18, wherein the adjustment component comprises a threaded bolt.
(Item 21)
20. The system of claim 18, wherein the receiving component is integral with the at least one ion source magnet.
(Item 22)
20. The system of claim 18, wherein the at least one ion source magnet is at least partially encapsulated in epoxy.
(Item 23)
20. The system of claim 18, wherein the at least one ion source magnet comprises two ion source magnets.
(Item 24)
20. The system of claim 18, wherein the at least one vertical opening comprises at least two, three, or four vertical openings.
(Item 25)
1. A method, comprising:
a) providing a system according to any one of items 18-24;
b) moving the at least one ion source magnet from a first position among the plurality of positions to a second position among the plurality of positions;
c) inserting the at least one adjustment component into the at least one receiving component through the at least one longitudinal opening;
d) fixing the at least one adjustment component to the at least one receiving component, thereby fixing the at least one ion source magnet in the second position.
(Item 26)
26. The method of claim 25, wherein the at least one ion source magnet comprises a first and a second ion source magnet, and both the first and second ion source magnets are moved from a first position to a second position and fixed at the second position.
(Item 27)
1. An article of manufacture comprising a metal assembly of an accelerator system for generating a high energy ion beam,
the metal assembly, when positioned within the accelerator system, i) partially intercepts the high energy ion beam; and ii) is within a vacuum environment;
The metal assembly comprises: i) at least one water cooling channel; and ii) a first metal component, a second metal component, and a filler metal, the filler metal attaching the first metal component to the second metal component at a joint.
(Item 28)
28. The article of manufacture of claim 27, wherein the first and second metallic components comprise highly thermally conductive metals.
(Item 29)
28. The article of manufacture of claim 27, wherein the filler metal has a lower melting point than the first and second metal components.
(Item 30)
28. The article of manufacture of claim 27, wherein the first metal component comprises a tube sheet and the second metal component comprises a tube plate.
(Item 31)
28. The article of manufacture of claim 27, wherein the filler metal comprises a BNi-7 alloy.
(Item 32)
28. The article of manufacture of claim 27, wherein the first metal component comprises a first item selected from the group consisting of a first tube, a tube cap, a different tube sheet, and a valve, and the second metal component comprises a second item selected from the group consisting of a second tube, a tube cap, a different tube sheet, and a valve.
(Item 33)
28. The article of manufacture of claim 27, wherein the at least one water cooling channel comprises at least two water cooling channels.
(Item 34)
1. A system comprising:
a) an accelerator system for generating a high energy ion beam;
b) a metal assembly; and
the metal assembly is positioned within the accelerator system, whereby the metal assembly i) partially intercepts the high energy ion beam; and ii) is within a vacuum environment;
The system, wherein the metal assembly comprises: i) at least one water cooling channel; and ii) a first metal component, a second metal component, and a filler metal, the filler metal attaching the first metal component to the second metal component at a joint.
(Item 35)
1. A method, comprising:
a) attaching a first metal component to a second metal component with a filler metal using a brazing technique to produce a metal assembly;
b) inserting the metal assembly into an accelerator system that generates a high energy ion beam;
The method, wherein the metal assembly is positioned to partially intercept the high energy ion beam.
(Item 36)
Item 36. The method of item 35, wherein the metal assembly further comprises at least one water cooling channel.
(Item 37)
Item 36. The method of item 35, wherein the metal assembly is further positioned so as to be in a vacuum environment.
(Item 38)
1. A system comprising:
a) a high voltage dome;
b) an ion source plasma chamber located inside the high voltage dome;
c) an extraction component operably coupled to the ion source plasma chamber; and
d) a gas removal subsystem, said gas removal subsystem comprising:
i) an exhaust component located inside the high voltage dome;
ii) an insulating hose, a first portion of the insulating hose being located inside the high voltage dome and a second portion of the insulating hose being located outside the high voltage dome in an area of lower voltage;
iii) a first vacuum pump located inside the high voltage dome and operably connected to the exhaust component and the extraction component, the first vacuum pump configured to remove gas from the extraction component and deliver the gas to the exhaust component; and
iv) a second vacuum pump located inside the high voltage dome and operably connected to the exhaust component; and a gas removal subsystem comprising:
the second vacuum pump is configured to receive the gas from the exhaust component at a first pressure and deliver the gas to the insulated hose at a second pressure, the second pressure being greater than the first pressure.
(Item 39)
e) an outer pressure vessel, wherein at least a portion of the high voltage dome, the ion source plasma chamber, the extraction component, the exhaust component, the first vacuum pump, the second pump, and the insulated hose are located within the pressure vessel.
(Item 40)
40. The system of claim 38, wherein the insulating hose is configured to vent the gas to atmosphere.
(Item 41)
40. The system of claim 38, wherein the gas is a non-ionized gas.
(Item 42)
42. The system of claim 41, wherein the non-ionized gas is deuterium gas.
(Item 43)
40. The system of claim 38, further comprising the gas.
(Item 44)
44. The system of claim 43, wherein the gas is a non-ionized gas.
(Item 45)
Item 39. The system of item 38, wherein the insulating hose has a helical shape.
(Item 46)
Item 46. The system of item 45, wherein the insulating hose has about 20-30 helical turns and is about 5-15 feet in length.
(Item 47)
40. The system of claim 38, wherein the first vacuum pump comprises a pump selected from a turbomolecular pump, a cryopump, an ion pump, and a high vacuum pump.
(Item 48)
Item 39. The system of item 38, wherein the second vacuum pump comprises a roughing pump.
(Item 49)
e) an inner pressure vessel located inside the high voltage dome, wherein the second vacuum pump is located in the pump pressure vessel, and the following components: the high voltage dome, the ion source plasma chamber, the extraction component, and the first vacuum pump are not located in the inner pressure vessel.
(Item 50)
1. A gas removal subsystem configured to be installed into a high energy ion beam generating system having a high voltage dome and an extraction component, the gas removal subsystem comprising:
a) an exhaust component configured to be positioned inside the high voltage dome;
b) an insulating hose, a first portion of the insulating hose configured to extend through an opening in the high voltage dome; and
c) a first vacuum pump configured to be located inside the high voltage dome and operably coupled to the exhaust component and the extraction component, the first vacuum pump configured to remove gas from the extraction component and deliver the gas to the exhaust component; and
d) a second vacuum pump configured to be located inside the high voltage dome and configured to be operably connected to the exhaust component;
a gas removal subsystem, the second vacuum pump configured to receive the gas from the exhaust component at a first pressure and deliver the gas to the insulated hose at a second pressure, the second pressure being greater than the first pressure.
(Item 51)
1. A method, comprising:
a) providing a system according to claim 50;
b) activating the gas removal subsystem;
The gas present in the extraction component is
i) removed by said first vacuum pump to said exhaust component;
ii) received by the second vacuum pump from the exhaust component at a first pressure and delivered to the insulating hose at a second pressure higher than the first pressure;
iii) delivered to atmosphere by said insulating hose;
method.
(Item 52)
52. The method of claim 51, wherein the gas in the extraction component is a non-ionized gas that travels to the extraction component from the ion source plasma chamber.
(Item 53)
1. A system comprising:
a) an outer pressure vessel;
b) an inner pressure vessel located inside the outer pressure vessel;
c) an exhaust component located inside the outer pressure vessel, a portion of the exhaust component also located within the inner pressure vessel; and
d) an insulating hose located inside the outer pressure vessel, a portion of the insulating hose also located within the inner pressure vessel; and
e) a first vacuum pump located inside the outer pressure vessel and operably connected to the exhaust component;
f) a second vacuum pump located inside the inner pressure vessel and operably connected to the exhaust component.
(Item 54)
54. The system of claim 53, wherein the outer pressure vessel comprises a gas at a higher pressure than the gas in the inner pressure vessel.
(Item 55)
54. The system of claim 53, wherein the gas in the inner pressure vessel is at about atmospheric pressure.
(Item 56)
54. The system of claim 53, wherein the first vacuum pump is configured to be operably coupled to an extraction component of an accelerator system that generates a high-energy ion beam, and the first vacuum pump is configured to remove gas from the extraction component and deliver the gas to the exhaust component.
(Item 57)
Item 57. The system of item 56, wherein the second vacuum pump is configured to receive the gas from the exhaust component at a first pressure and deliver the gas to the insulated hose at a second pressure, the second pressure being greater than the first pressure.
(Item 58)
54. The system of claim 53, further comprising an extraction component.
(Item 59)
60. The system of claim 58, further comprising an ion source plasma chamber located inside the outer pressure vessel.
(Item 60)
60. The system of claim 59, wherein the extraction component is operably coupled to the ion source plasma chamber.
(Item 61)
1. A system comprising:
a) at least one high voltage component held at a high voltage in an accelerator system that generates a high energy ion beam;
b) a power component electrically coupled to the at least one high voltage component;
the power component provides power to the at least one high voltage component;
the power component comprises a V-belt;
The system wherein the V-belt comprises a plurality of sections that are i) poor electrical conductors or ii) non-electrical conductors.
(Item 62)
62. The system of claim 61, wherein the V-belt comprises a polyester polyurethane composite material.
(Item 63)
62. The system of claim 61, wherein the power components further comprise a motor and a generator.
(Item 64)
Item 62. The system of item 61, wherein the power components further comprise a first V-belt pulley operably attached to the motor and a second V-belt pulley operably attached to the generator.
(Item 65)
62. The system of claim 61, wherein the at least one high voltage component comprises an ion source plasma chamber.
(Item 66)
1. A system comprising:
a) an accelerator subsystem for generating a high energy ion beam, said accelerator subsystem comprising:
i) an ion source plasma chamber;
ii) a microwave generating component that generates microwaves; and
iii) a power source operably coupled to said microwave generating component; and
iv) a waveguide positioned to receive the microwaves and deliver them to the ion source plasma chamber, where the microwaves contact a gas in the ion plasma chamber to generate an ion source; and
v) an ion beam extraction component operatively coupled to the ion source plasma chamber for extracting a low energy ion beam from the ion plasma chamber;
iv) an accelerator subsystem comprising an accelerator column and an accelerator component comprising an accelerator entrance aperture for receiving the low energy ion beam and an accelerator exit aperture for delivering the high energy ion beam;
b) a power modulation component operably coupled to the power source;
The power modulation component is configured to modulate the power flowing from the power source to the microwave generating component, whereby the microwaves incident on the waveguide are rapidly pulsed and/or extinguished/generated, thereby rapidly pulsing and/or extinguishing/generating the high energy ion beam.
(Item 67)
68. The system of claim 66, wherein the accelerator system is a direct injection accelerator system.
67. The system of claim 66, wherein the microwave generating component comprises a magnetron.
(Item 69)
1. A method, comprising:
a) providing a system according to claim 66;
b) activating the accelerator subsystem and the power modulation components such that the high energy ion beam is generated, rapidly pulsed, and/or extinguished/generated.
(Item 70)
1. A method, comprising:
a) in a direct injection accelerator system for generating a high energy ion beam, positioning an ion beam generating component at a first distance from an accelerator inlet of an accelerator column;
b) positioning the ion beam generating component at a second distance from an accelerator inlet of an accelerator column;
The method, wherein the second distance is different from the first distance, and the second distance improves performance of the direct injection accelerator system.
(Item 71)
Item 71. The method of item 70, wherein the first and second distances are in the range of 20 to 500 mm.
(Item 72)
1. A system comprising:
a) a direct injection accelerator subsystem for generating a high energy ion beam, said accelerator system comprising:
i) an ion source plasma chamber;
ii) a microwave generating component that generates microwaves; and
iii) a power source operably coupled to said microwave generating component; and
iv) a waveguide positioned to receive the microwaves and deliver them to the ion source plasma chamber, where an ion beam is generated when the microwaves contact a gas in the ion plasma chamber; and
v) an extraction component operably connected to the ion source plasma chamber; and
iv) an accelerator component comprising an accelerator column and an accelerator entrance aperture for receiving the ion beam;
b) a vacuum component; and
The system, wherein the vacuum component is operably coupled to the extraction component and/or the accelerator component, and the vacuum component is configured to reduce pressure within the extraction component and/or the accelerator component.
(Item 73)
73. The system of claim 72, wherein the reduction in pressure is at a level that reduces a diameter of the high energy ion beam.
(Item 74)
1. A method, comprising:
a) providing a system according to claim 72;
b) activating the direct injection accelerator subsystem and the vacuum components such that the high energy ion beam is generated;
The method, wherein the energetic ion beam has a smaller diameter than it would have in the absence of the reduction in pressure.
(Item 75)
1. A system comprising:
a) an accelerator subsystem for generating a high energy ion beam, said accelerator subsystem comprising:
i) a high voltage dome;
ii) an ion beam generating component located inside the high voltage dome;
iii) an accelerator component comprising an accelerator column; and
b) a water resistor subsystem; and
The water resistor subsystem comprises:
i) a water circulation component comprising a water piping and a water reservoir;
ii) a water resistor element extending along the accelerator column;
The system, wherein the water resistor element comprises non-conductive tubing fluidly connected to or integral with the water piping, whereby controlled conductivity water circulating within the water circulation component passes through the water resistor element.
(Item 76)
Item 76. The system of item 75, further comprising the controlled conductivity water, the controlled conductivity water comprising: i) deionized water; and 2) a deionizing (DI) resin and a metal salt.
(Item 77)
76. The system of claim 75, wherein the accelerator component further comprises a plurality of grading rings extending along the accelerator column.
(Item 78)
79. The system of claim 75, wherein the insulating tubing comprises a material selected from the group consisting of polycarbonate, polymethylmethacrylate (PMMA), and polyethylene.
76. The system of claim 75, wherein the water circulation components further comprise a water pump and a heat exchanger.
(Item 80)
76. The system of claim 75, wherein the controlled conductivity water comprises a sufficient amount of the DI resin such that the deionized water has a resistivity of 15 megaohm-cm or greater.
(Item 81)
76. The system of claim 75, wherein the metal salt is selected from the group consisting of copper sulfate, sodium chloride, ammonium chloride, magnesium sulfate, and sodium thiosulfate.
(Item 82)
76. The system of claim 75, wherein the water resistor element can withstand voltages up to about 300 kV DC and remove heat up to about 3 kW.
(Item 83)
1. A method, comprising:
a) providing a system according to claim 75;
b) activating the accelerator subsystem and the water resistor subsystem;
The method of claim 1, wherein the controlled conductivity water circulates through the water circulation component while the high energy ion beam is being generated, and the water resistor element functions as an electrical resistor along the accelerator column.
(Item 84)
1. A system comprising:
a) at least one high voltage power supply (HVPS) configured to deliver power to components of an accelerator subsystem that generates a high energy ion beam;
b) a water resistor subsystem; and
The water resistor subsystem comprises:
i) a water circulation component comprising a water piping and a water reservoir;
ii) a water resistor element comprising insulating tubing;
the insulating tubing is fluidly connected to or integral with the water piping, whereby controlled conductivity water circulation within the water circulation component passes through the water resistor element;
system.
(Item 85)
1. A method, comprising:
a) providing a system according to claim 84;
b) testing the at least one HVPS using the water resistor subsystem as a test load.
(Item 86)
1. A method of designing a lens, the method comprising:
a) inputting the following parameters at the plasma lens aperture of the accelerator system into a software application: beam current, extraction voltage, ion species ratio, maximum electric field, and ion current density;
b) receiving an output from the software for the design of at least one lens in an electrostatic lens stack, the electrostatic lens stack comprising a plasma lens, an extraction lens, a suppression lens, and an exit lens;
and c) fabricating the at least one lens based on the output.
(Item 87)
87. The method of claim 86, wherein the software application comprises a PBGUNS software application.
(Item 88)
89. The method of claim 86, wherein the at least one lens comprises at least two, at least three, or all four of the lenses in the electrostatic lens stack.
87. The method of claim 86, further comprising inputting at least one of a grid accuracy, an empirically determined beam neutralization factor, and electron and ion temperatures in the source plasma into the software application.
(Item 90)
1. A high energy ion beam generator system comprising an extraction lens stack having a plurality of insulating balls positioned between lens gaps of the extraction lens stack.
(Item 91)
Item 91. The system of item 90, wherein three insulating balls are positioned between each lens gap.
(Item 92)
Item 92. The system of item 91, wherein the three insulating balls are evenly spaced in azimuth coordinates.
(Item 93)
Item 91. The system of item 90, wherein the lens stack is held together using metal bolts.
(Item 94)
Item 91. The system of item 90, wherein the insulating ball is an alumina ceramic ball.
(Item 95)
95. A method for generating neutrons or protons comprising using a system according to any of items 90-94.
(Item 96)
1. A neutron generator system, comprising:
a) a high power density solid target comprising reactive hydrogen species embedded in a solid matrix;
b) a cooling component.
(Item 97)
97. The system of claim 96, wherein the solid matrix comprises titanium.
(Item 98)
97. The system of claim 96, wherein the reactive hydrogen species is deuterium.
(Item 99)
97. The system of claim 96, wherein the reactive hydrogen species is tritium.
(Item 100)
97. The system of claim 96, wherein the cooling component is a closed loop component.
(Item 101)
97. The system of claim 96, wherein the cooling component comprises a coolant source.
(Item 102)
Item 102. The system of item 101, wherein the coolant is water.
(Item 103)
97. The system of claim 96, wherein the target has a wall thickness of 0.02 inches or less.
(Item 104)
Item 104. The system of item 103, wherein the wall thickness is 0.01 inches or less.
(Item 105)
105. The system of claim 103 or 104, wherein the wall is constructed of a material selected from the group consisting of copper, silver, gold, diamond, diamond-like carbon, or combinations thereof.
(Item 106)
97. The system of claim 96, wherein the target comprises a swirl that increases the surface area relative to a target lacking the swirl.
(Item 107)
Item 107. The system of item 106, wherein the volute is selected from the group consisting of fins and ribs, or combinations thereof.
(Item 108)
Item 101. The system of item 100, wherein the closed loop component comprises a deionization subcomponent.
(Item 109)
101. The system of claim 100, wherein the closed loop component comprises a filtration subcomponent.
(Item 110)
97. The system of claim 96, wherein the cooling component is configured for laminar flow of coolant.
(Item 111)
97. The system of claim 96, wherein the cooling component comprises channels having irregular surface features.
(Item 112)
Item 112. The system of item 111, wherein the irregular surface features are selected from the group consisting of dimples and spiral depressions, or combinations thereof.
(Item 113)
97. The system of claim 96, wherein the coolant component comprises a cooling device positioned to pre-cool the coolant prior to contact with the target.
(Item 114)
A method for generating neutrons using a high power density solid target comprising the use of a system according to any of claims 96-113.
(Item 115)
1. A system, the system being part of or for use in a neutron generator system, the system comprising:
A system comprising: a) a solid target; b) a vacuum system; and c) a noble gas source in fluid communication with the vacuum system and configured to emit a noble gas in a vicinity of the solid target.
(Item 116)
Item 116. The system of item 115, wherein the noble gas is argon.
(Item 117)
1. A method of purifying a neutron generator solid target, the method comprising exposing the solid target to a noble gas while the solid target is exposed to an ion beam.
(Item 118)
Item 118. The method of item 117, wherein the noble gas is argon.
(Item 119)
Item 118. The method of item 117, wherein the noble gas is flowed at 1 to 10 cubic centimeters per minute.
(Item 120)
1. A neutron generator system, comprising:
1. A neutron generator system comprising: a) an accelerator that produces an ion beam; b) a gas target positioned to be contacted by the ion beam; c) a target aperture separating the accelerator and the gas target; d) a steering component that focuses the ion beam into the aperture; and e) a plurality of thermal sensors positioned near an upstream-facing surface of the target aperture.
(Item 121)
Item 121. The system of item 120, wherein the plurality of thermal sensors comprises four thermal sensors equally spaced at 90 degree intervals around the axis of the aperture.
(Item 122)
Item 121. The system of item 120, wherein the sensor comprises a thermocouple.
(Item 123)
Item 123. The system of item 122, wherein the thermocouple is a copper-constantan thermocouple.
(Item 124)
Item 121. The system of item 120, wherein the sensor is selected from the group consisting of a platinum resistance temperature detector (RTD), a thermistor, and a semiconductor temperature sensor.
(Item 125)
Item 121. The system of item 120, further comprising a processor receiving a temperature signal from the sensor.
(Item 126)
Item 126. The system of item 125, wherein the processor sums temperature signals from the sensors to generate an average target aperture temperature.
(Item 127)
127. The system of claim 126, wherein the processor adjusts the ion beam position based on the average target aperture temperature to minimize a temperature of the target aperture.
(Item 128)
129. A method of steering an ion beam to a target aperture in a neutron generator system, the method comprising: a) measuring temperature at a plurality of locations around the target aperture; and b) steering the ion beam to minimize the temperature at the target aperture.
1. A neutron generator system comprising: a) an accelerator that produces an ion beam; b) a gas target positioned to be contacted by the ion beam; c) a target aperture separating the accelerator and the gas target; and d) a reverse gas jet that increases a pressure differential across the aperture.
(Item 130)
Item 130. The system of item 129, wherein the reverse gas jet comprises a nozzle that converges and then diverges.
(Item 131)
Item 130. The system of item 129, wherein the reverse gas jet comprises a nozzle opening of about 3/8 inch.
(Item 132)
Item 132. The system of item 131, wherein the reverse gas jet has a narrow section gap of less than 0.01 inches.
(Item 133)
Item 133. The system of item 132, wherein the reverse gas jet has a nozzle angle of 12.5 degrees.
(Item 134)
1. A method of increasing a pressure differential across a target opening of a neutron generator, the method comprising employing reverse gas injection at the target opening.
(Item 135)
1. A neutron generator system comprising a beam scraper, the beam scraper being movable into the path of an ion beam using a motor, the motor being mounted to the generator system outside a vacuum vessel containing a target.
(Item 136)
Item 136. The system of item 135, wherein the motor is connected to the beam scraper via a magnetically coupled vacuum feedthrough.
(Item 137)
Item 136. The system of item 135, wherein the motor, beam scraper, and connections therebetween are all metal with brazing fabrication.
(Item 138)
1. A method for blocking a portion of an ion beam striking a target in a neutron generator, the method comprising: moving a beam scraper using a motor to a position where it will be contacted by the ion beam, the motor being mounted on the generator system outside a vacuum vessel containing the target.
(Item 139)
1. A system comprising:
a) a high energy ion beam generator device having a first interlock;
b) a user control station having a second interlock;
The system, wherein the high energy ion beam generator and the user control station are connected via a fiber optic interlock, the fiber optic interlock comprising a number of normally closed switches in a series loop that remain closed to indicate that the generator is safe to operate, a number of normally open switches in a parallel loop that remain open to indicate that the generator is safe to operate, or both the series loop and the parallel loop.
(Item 140)
Item 140. The system of item 139, wherein the high energy ion beam generator and the user control station are electrically isolated from each other.
(Item 141)
Item 140. The system of item 139, wherein the fiber optic interlock comprises a frequency generator.
(Item 142)
Item 142. The system of item 141, wherein the frequency generator triggers a fiber optic transmitter to cause light to pulse at a set frequency.
(Item 143)
Item 140. The system of item 139, wherein the system includes control software that manages the fiber optic interlock.
(Item 144)
144. The system of claim 143, wherein the control software operates a multi-signal verification procedure for the fiber optic interlock.
(Item 145)
A method, the method including transmitting information from the high energy ion beam generator to the user control station or transmitting information from the user control station to the high energy ion beam generator using a system described in any of claims 139-144.
(Item 146)
1. A system comprising:
a) a high energy ion beam generator device for generating a beam;
b) a damage mitigation component; and
The damage mitigation component comprises:
i) a number of sensors positioned on the device and configured to monitor a number of areas of the device that may interact with the beam;
ii) control software configured to communicate with the plurality of sensors, generate alerts or alarms, and adjust the device in response to the alerts or alarms.
(Item 147)
Item 147. The system of item 146, wherein one or more of the plurality of sensors measures a temperature in an area of the device.
(Item 148)
Item 147. The system of item 146, wherein one or more of the plurality of sensors measures a coolant flow rate.
(Item 149)
Item 147. The system of item 146, wherein the sensor is in a continuous sensing mode.
(Item 150)
Item 147. The system of item 146, wherein each sensor has a threshold associated with it that, if exceeded, generates the alert or alarm.
(Item 151)
Item 147. The system of item 146, wherein the alert comprises a user warning.
(Item 152)
Item 147. The system of item 146, wherein the alarm triggers a device shutdown.
(Item 153)
Item 147. The system of item 146, wherein the alarm is a latch arm that requires the user to reset the device prior to further action.
(Item 154)
147. The system of claim 146, wherein the control software filters out EMI.
(Item 155)
Item 155. The system of item 154, wherein the rejected EMI is below a predetermined threshold duration or frequency.
(Item 156)
156. A method comprising detecting a potentially damaging event to a high energy ion beam generator device using a system according to any of claims 146-155.
(Item 157)
1. A system comprising:
a) a high energy ion beam generator device;
b) an arc-down mitigation component; and
The arc-down mitigation component comprises:
i) a plurality of sensors positioned on the device and configured to monitor for conditions consistent with an arc-down event;
ii) control software configured to communicate with the plurality of sensors, generate alerts or alarms, and adjust the device in response to the alerts or alarms.
(Item 158)
158. The system of claim 157, wherein the alarm triggers an automatic recovery sequence that returns the device to normal operation without user intervention.
(Item 159)
159. A method comprising: responding to an arc down event using a system according to any of claims 157-158.
(Item 160)
A high energy ion beam generator system comprising closed loop control components that govern i) high voltage power supply (HVPS) setpoints and/or ii) ion source current setpoints.
(Item 161)
A method for controlling neutron flux output variability in a high energy ion beam generator comprising: i) managing high voltage power supply (HVPS) setpoints using closed loop control components; and/or ii) managing ion source current setpoints.
(Item 162)
1. A neutron collimator for use in neutron radiography, the neutron collimator comprising a high density polyethylene (HDPE) layer, a borated polyethylene layer, a metal layer, and a cadmium layer.
(Item 163)
163. A system for thermal neutron radiography comprising: a) a neutron source; b) a neutron collimator according to item 162; and c) a detector.
(Item 164)
Item 164. The system of item 163, wherein the collimator is offset so that it is not directly aligned with the fast neutron source.
(Item 165)
165. A method for imaging a sample, the method comprising exposing the sample to neutrons generated by a system according to claim 163 or 164.
(Item 166)
A semiconductor manufacturing system or method comprising an accelerator system that generates a high-energy ion beam according to any one of claims 1-165, the accelerator system directing the beam toward a component that holds a semiconductor material.
(Item 167)
A method for manufacturing a semiconductor wafer comprising contacting a semiconductor material with protons generated from a high energy ion beam generator system or method according to any of claims 1-165.
(Item 168)
Item 168. The method of item 167, further comprising the step of producing a thin film wafer by fracturing the semiconductor material.
(Item 169)
Item 169. The method of item 168, further comprising the step of fabricating a photovoltaic (PV) wafer from the thin film wafer.
(Item 170)
Item 170. The method of item 169, further comprising the step of fabricating a solar panel comprising the photovoltaic wafer.
(Item 171)
Item 169. The method of item 168, further comprising fabricating light emitting diodes (LEDs) from the thin film wafer.

FIG. 1 shows an exemplary schematic diagram of an accelerator system in which the target is a gas target. FIG. 2 shows an exemplary schematic diagram of an accelerator system in which the target is a solid target. Figures 3A-B show a known waveguide design with metallic impedance matching components (two step ridges are shown) each extending inwardly from the wider face of the waveguide in the direction of its narrower dimension, Figure 3A is a cross-sectional view, while Figure 3B shows the electric field at each step. 4A-B show an example waveguide design of the present disclosure with an inverse impedance matching component that extends progressively outward from the midplane of the waveguide towards the wider walls of the waveguide, with FIG 4A being a cross-sectional view, while FIG 4B shows the electric field at each stage. FIG. 5 shows an example layout of telemetry and diagnostics in an accelerator system. FIG. 6 shows an exemplary flow chart for automatic mapping (left) and closed-loop feedback (right). FIG. 7 shows an example of a 2D slice of the ion source operating phase space that is mapped by the automated algorithm. FIG. 8 provides an exemplary embodiment of an adjustment system for adjusting and fixing the solenoid magnet surrounding the ion source plasma chamber. 9A shows an example differential tube assembly with the parts brazed together, FIG 9B shows a perspective view of an example differential tube sheet showing the water channels located therein, and FIG 9C shows a perspective view of an example differential tube sheet. FIG. 10 provides an example schematic diagram of gas pumping flow in a nested pressure vessel configuration, where the roughing pump is located inside an inner (smaller) pressure vessel inside an outer (larger) pressure vessel, whereby the roughing pumps can operate at different pressures (e.g., atmospheric pressure). FIG. 11 shows an example of a pulsed beam from a modulating magnetron modulating the microwaves entering the plasma chamber (as measured using a Faraday cup). FIG. 12A shows an example of a simulation of the beam trajectory in a direct injection high gradient accelerator. 70 mA deuterium, 300 keV accelerator, 39 kV extraction. The resulting beam generally has a lower emittance but a larger divergence. FIG. 12B shows an example of a simulation of the same beam with drift length and electrostatic suppression and drift region before a low gradient accelerator. 70 mA deuterium, 300 keV accelerator, 39 kV extraction. The resulting beam generally has a lower emittance but a lower divergence. FIG. 13 illustrates an exemplary actively cooled water resistor system. FIG. 14 shows an exemplary user interface for a lens design software application. FIG. 15 shows a sample beam trajectory plot from PBGUNS. FIG. 16 illustrates an exemplary use of precision ceramic balls for electrical isolation and alignment of electronic restraining elements. 17 shows an embodiment of a liquid-cooled solid target featuring turbulence-inducing structures, including multiple parallel fins with recessed holes to interrupt a smooth surface. The left panel shows a top view. The right panel shows a cross-sectional view with the cross-sectional plane identified. FIG. 18 shows an example of irregular features that induce turbulence in the fluid cooling channels of a solid target. FIG. 19 shows a graph of neutron yield from a titanium plated target as a function of time. FIG. 20 illustrates an example configuration of a system for focusing and/or steering an ion beam through a target aperture. FIG. 21 shows a schematic diagram of reverse gas flow injection. FIG. 22 shows an example beam scraper configuration. FIG. 23 illustrates an exemplary fiber optic interlock arrangement for communication between an electrically isolated high energy ion beam generator and a user control station. FIG. 24 shows a schematic diagram of a moderator, collimator, and imaging enclosure for thermal neutron radiography applications.

Exemplary components of the accelerator system are described in more detail in the following sections: I. Ion Source, II. Infrastructure, III. High Voltage System, IV. Neutron Generating Target, V. Automatic Control System, VI. Diagnostics, and VII. Uses for the Accelerator System.

I. ION SOURCE
The ion source provided herein includes several components, including a plasma chamber microwave waveguide feed, operational parameter optimization techniques, a source magnet mounting mechanism, and the use of brazing to fabricate water-cooled beamline components. Each of these improvements will be discussed in turn.

A. "Inverse" Waveguides
Provided herein are waveguides that include inverse impedance matching components (e.g., inverted in the sense that the step ridges are mounted in the center of the waveguide rather than built into the external structure) that help prevent backflow of electrons when positioned between an electromagnetic wave source (e.g., a microwave source) and a plasma chamber (e.g., as part of a larger accelerator system). The inverse impedance matching components are generally considered to be "inverse" or "inside out" with respect to conventional prior art impedance matching techniques because, in one embodiment, the inverse components extend gradually outward from the midplane of the waveguide toward the wider walls (FIG. 4). In an embodiment, the reverse waveguide comprises a device comprising: a) a waveguide having i) a proximal end having an electromagnetic wave entry point, ii) a distal end having an electromagnetic wave exit point, and iii) an outer wall extending between the proximal and distal ends and configured to propagate electromagnetic waves; and b) an inverse impedance matching component located inside the waveguide component, wherein the inverse impedance matching component extends from the distal end of the waveguide at least part way towards the proximal end of the waveguide, the inverse impedance matching component having a distal end and a proximal end, the distal end of the impedance matching component being located at or near the distal end of the waveguide and having a larger cross-sectional area than the proximal end of the inverse impedance matching component.

In a microwave ion source, a plasma chamber is supplied with the desired gas (e.g., hydrogen, deuterium, etc.), a magnetic field, and microwave power. The microwaves are delivered to the plasma chamber through a waveguide that enters the chamber at the end opposite the beam exit aperture. The magnetic field is shaped so that the electron cyclotron resonance (ECR) condition is satisfied in the vicinity of the beam exit aperture, i.e., the electron cyclotron frequency at that location matches the frequency of the applied microwaves. For example,


where q is the electron charge, B is the magnetic flux density, and m is the mass of the electron.

Due to the magnetic field geometry, microwave power may also be absorbed in the ECR region within the waveguide before reaching the plasma chamber. This is prevented by keeping the waveguide under vacuum and isolating it from the gas in the plasma chamber using a ceramic disk. In the art, the waveguide may include a mechanism for impedance transformation in the form of a pair of stepped ridges that increase in extent from the broad face of the guide to reach their maximum at the ceramic disk, designed to reduce the impedance mismatch between the waveguide and the plasma in the source chamber (see Figure 3).

By way of background, electrons created in the extraction and acceleration region of the accelerator system can enter the ion source plasma chamber through the ion beam exit aperture and strike the ceramic insulator at the opposite end of the plasma chamber with high energy. If these electrons burn holes through the insulator, the working gas in the plasma can flow into the waveguide where it can absorb microwaves and result in plasma formation in this region. This reduces the microwave power available to drive the ion source plasma, affecting the stability of the ion source and lowering the maximum extractable beam current. If the holes in the ceramic become large enough, overheating of the waveguide can also damage its components and affect the overall system reliability and lifespan.

The reverse waveguide described herein (e.g., FIG. 4) is designed to intercept backflowing electrons that may perforate the ceramic disk, which would otherwise lead to plasma formation in the waveguide, reducing the plasma density and beam current in the source chamber due to loss of microwave power, while possibly damaging the waveguide due to excessive heating. In certain embodiments, holes are provided in the ceramic disk so that the electrons do not damage the disk by damaging it, but instead intentionally affect the impedance matching component directly.

Thus, in some embodiments, provided herein is an inverse impedance matching component (e.g., a water-cooled metal surface) positioned to efficiently couple microwave power into the plasma chamber while intercepting backflow electrons without damage. Known designs of waveguide step ridges are conventional in that they are electrically and mechanically attached to the outer waveguide wall and extend symmetrically from the center of its broad face into the guide, spanning a portion of the width of the guide, as shown in FIG. 3. Due to the orientation and symmetry of the electric field within the waveguide, in some embodiments it is possible to split it in half along the mid-plane between the ridges and transpose the two halves across the mid-plane, as illustrated in FIG. 4. This symmetry is applied at each step of the ridges, maintaining the electrical performance of the stepped design and matching the impedance of the waveguide to the plasma chamber. Other approaches may also be used to reverse the typical orientation of the impedance matching components within the waveguide.

The resulting inverted design provided herein provides a substantial metal mass (see large cross-sectional area, rightmost portion of FIG. 4B) in the path of the backflowing electrons on the axis of the plasma chamber, supported from the sides of the chamber by support components that are in a low electric field region and therefore do not perturb microwave propagation. These support components (e.g., legs) can be, for example, solid metal for low power applications, or hollow tubes for water cooling impedance matching components, which can be, for example, in the form of discrete steps as shown, or in the form of smoothly tapered shapes.

In some embodiments, two sets of support legs are used as shown in FIG. 4A, with separation so that reflection of microwave power away from the plasma chamber by one support leg is largely cancelled by the power reflected by the other support leg, with the second reflection having equal wave magnitude and opposite wave phase. Alternatively, in some embodiments, where reflection magnitude is not important in low power applications, a single support leg may be used.

In some embodiments, the face of the impedance matching component on which the backflow electrons are incident can be equipped with a refractory metal insert for high power applications, or left as a lower melting point, high thermal conductivity metal in low power applications, as desired.

In the prior art, each of the impedance matching components (which may consist, for example, of two sets of metal steps (step ridges)) extends inward from the wider face of the waveguide in the direction of its narrower dimension, with each half of the half being translated inward by half of the narrow dimension of the waveguide (Figure 3).

(B. Operational Parameter Optimization)
In an embodiment, the accelerator system or subsystem described herein is optimized to improve performance. In general, an accelerator system consists of a number of coupled nonlinear subsystems. These include, but are not limited to, ion source magnet position and current, ion source microwave power, ion source gas flow, beam extraction voltage, accelerator voltage, focusing solenoid current, steering magnet current, and gas target pressure. The entire system is generally too complex to be directly modeled or predicted a priori. In addition, slight differences between individual instances of the system, such as beamline alignment, can have a large impact on system performance and are difficult to incorporate into predictive models. Thus, final system optimization usually relies on empirical results. This process generally requires a skilled and experienced operator to obtain peak performance of the system, with the risk of component damage due to operator error. An embodiment of the present disclosure addresses these issues by providing an automatic and partially automatic process for optimization.

An automated process for the final optimization of the system provides repeatable performance while minimizing the risk of damage and eliminating the need for a skilled operator. In an embodiment, the accelerator system or subsystem may include one or more protection/monitoring components, including, but not limited to, thermocouples, cameras, and voltage and current monitors, that automatically assess the state of the system and prevent it from operating in conditions that may damage the components during the optimization process. FIG. 5 provides exemplary protection and monitoring components, including ion source mass flow meters and pressure gauges, ion source thermocouples and coolant flow meters, focusing solenoid thermocouples, coolant flow meters, voltage monitors, and current monitors, aperture cameras, thermocouples, and coolant flow meters, target cameras, thermocouples, coolant flow meters, and radiation detectors, extraction and suppression pressure gauges, thermocouples, current monitors, and voltage monitors, beam diagnostic components such as current monitors and emittance scanners, pressure gauges, and gas analyzers.

In an embodiment, these monitoring components communicate with a central computer-driven control software that allows for automatic adjustments to the monitored accelerator system components. For example, during this process, one or more system parameters are automatically controlled and adjusted while the associated system outputs are monitored. This allows the operating phase space of the individual systems to be mapped. Such a map allows the most stable operating points to be found throughout the range of the system. Once mapped, the control system can automatically use a closed loop PID (proportional-integral-derivative) algorithm to return to these stable operating points as needed, without the need for a skilled operator. One example of computer-implemented control logic that provides feedback from the monitoring components to a central computer system and prevents parts of the accelerator system from operating in conditions that may damage various components is shown in FIG. 6.

In some embodiments, the ion source subsystem is monitored using a monitoring component. Initially, prior to implementing the monitoring component, each parameter, such as the ion source magnet position and current, ion source microwave power, ion source gas flow, and extraction voltage, was manually and individually adjusted while performance metrics such as beam current were recorded. This resulted in a limited mapping of the operating phase space. This manual process was time consuming and only a small subset of the operating space could be pursued at a reasonable period. Manual methods are also prone to damaging components, especially when an automatic health monitoring and interlock system is not implemented. To begin to address these limitations, algorithms (such as those in FIG. 6 ) were developed to post-process data collected during such manual optimization runs and map the operating phase space, as illustrated by the example shown in FIG. 7 . This partial automation improved the efficiency and repeatability of the process, but does not allow for real-time results while the system is operating. In some embodiments, a monitoring component, employed to track long-term operation at a given set point and collect long-term stability statistics, can also be incorporated into the system to quantitatively determine the most stable operating point.

(C. Magnet concentration/installation)
Since a precise magnetic field profile in the ion source is a critical factor for proper coupling of microwave power into the plasma, small physical movements of the ion source magnets can cause large changes in source performance. Therefore, adjustment systems and components are provided herein to adjust and fix the location of these magnets as required for testing and optimization, as well as to account for subtle variations due to the system. An exemplary embodiment of an adjustment system for adjusting and fixing the solenoid magnets surrounding the ion source plasma chamber is shown in FIG. 8. In this embodiment, each ion source solenoid magnet is fixed to a magnet by a single The magnet is encapsulated in an epoxy that is used to tightly attach to one or more mounting components (e.g., threaded metal features). The magnet focuses the magnetic field in the ion source region and insulates the ion source from any external magnetic fields. The magnet assemblies are located inside a ferromagnetic enclosure that shields the magnets from the magnetic field. The ferromagnetic enclosure has slots along its sides to allow for the attachment of bolts from outside the enclosure to threaded metal features on each magnet assembly. . The location of each magnet along the axis of the source shaft can thus be adjusted by moving the bolt along the slot and fixed in position by tightening the bolt against the enclosure. Provided herein is a reliable and relatively low cost method and system for both positioning and fixing an ion source solenoid magnet in a fixed position.

D. Brazing and Water Cooling
In an embodiment, provided herein is a metal assembly (e.g., comprised of a low conductance metal) that partially blocks a high-energy ion beam when positioned in an accelerator system, the metal assembly comprising: i) at least one water-cooled channel; and ii) a first metal component, a second metal component, and a filler metal that attaches the first metal component to the second metal component at a joint (e.g., a brazed joint).

In configurations (e.g., with gaseous targets), a large pressure differential across the vacuum system is maintained by a low-conductance metal aperture that limits gas flow from the target to the beamline. High-energy ions in the edge regions of the ion beam deposit a large amount of energy on the aperture, which can lead to excessive heating and permanent damage.

Figure 9A shows an example differential tube assembly with the parts brazed together. Figure 9A shows the following parts: differential tube sheet (1), first differential tube (2), second differential tube (3), turbo shadow (4), open tube cap (5), a pair of open tube rods (6), and multiple plate plugs (7). Figure 9B shows a perspective view of an example differential tube sheet showing the water channels located therein. Figure 9C shows a perspective view of an example differential tube sheet.

Studies conducted during the development of the embodiments disclosed herein identified water cooling as an efficient method for removing heat from metal components that may partially obstruct the beam. Due to the high power density of the beam and the vacuum environment in which the beam and these components reside, special considerations must be taken into account when implementing water cooling.

The reliability of the system has been found to improve significantly by using highly thermally conductive metals (e.g., copper, aluminum) and machining the components that may be affected by the beam, and by adding water cooling channels to these parts to prevent them from melting. Because these components often do not need to have complex geometries, and highly thermally conductive materials are difficult to weld, it has been determined that brazing is the best way to join the parts together while leaving space for water to flow in. This not only allows the water channel geometry to be complex and reach all critical areas, but also creates a strong, full through joint that maintains the high thermal conductivity of the base metal. While more expensive than some other techniques, this provides high reliability against water leakage, which is very problematic for water-cooled parts that are in a vacuum.

First, note that in studies conducted during the development of the embodiments described herein, these components were made from copper, tungsten, aluminum, or stainless steel, but did not survive for long periods of time because there was no cooling, even if they only blocked the edges of the beam. Water-cooled channels were later added and sealed with NPT plugs, but the thread sealant was not effective in preventing leakage into the high vacuum environment because the temperature was high enough to decompose the polymer. O-rings have similar problems with high temperatures. Brazing metal plugs in place (e.g., to fill holes drilled to create water channels) is a good solution. In some embodiments, heat pipes are employed to remove waste heat rather than or in addition to water channels. In certain embodiments, the reliability of the overall accelerator system is improved by using brazed assemblies with water-cooled channels, since there may be fewer leaks that could damage other expensive equipment, such as vacuum pumps.

II. Ion Source Infrastructure
In certain embodiments, the ion source infrastructure has several improvements that contribute to its improved behavior. These include, for example, the implementation of vacuum pumps at high voltages, nested pressure vessels for operation of certain components at high voltages, and the use of V-belts for power transmission to components at high voltages. Each of these improvements will be discussed in turn.

A. Vacuum Pumps at High Voltage
A portion of the gas delivered into the plasma chamber is not ionized by the microwaves and drifts into the extraction and acceleration regions where a strong electric field is applied. The presence of neutral gas usually increases the likelihood of high voltage arcing, which can disrupt the operation of the system, induce fault conditions in the high voltage power supplies, and reduce the life of beamline components. Furthermore, ions in the beam can undergo atomic and molecular processes with the background neutral gas, such as scattering or charge exchange events, that degrade the beam quality or reduce the ion current.

In light of these problems, systems and methods are provided herein that allow for the removal of non-ionized gas from the extraction region. In an embodiment, the ion source region is designed to allow for a first vacuum pump (e.g., a small turbomolecular vacuum pump) to be mounted inside the high voltage dome, directly above the ion source, to remove gas entering the extraction region from the plasma source. However, the exhaust from the vacuum pump cannot be vented into the high pressure insulating gas-filled enclosure in which the ion source resides. To solve this secondary problem, the vacuum pump exhaust is compressed to a higher pressure using a second vacuum pump (e.g., a small roughing pump) and then passed into an insulating hose that extends between the high voltage end and ground. In an embodiment, the insulating hose is wound in a helical shape to increase its voltage breakdown rating. At the ground end, the gas is vented to the atmosphere as in a normal vacuum pump system. Pumping exhaust gas across a high voltage is uncommon and the solution is counter-intuitive due to the difficulty of implementation, but when using an insulating gas-filled enclosure, it allows for the removal of gas from the extraction and acceleration region. Pumping directly over the ion source region removes most of the leakage gas from the plasma source and reduces the pressure in the extraction region. This increases the maximum voltage that can be used, reduces arcing, increases long term reliability and allows for better beam quality. This also allows the ion source region to be designed regardless of gas flow requirements, increasing design flexibility.

Note that prior art designs used a vacuum pump at the grounded end of the accelerator, but gas is typically injected at the ion source end, which is held at a high voltage. In that configuration, the ion source and accelerator had to be carefully designed to have high gas flow and allow the gas to escape the accelerator. Even with such a design, the fundamental physics of the system limited the vacuum level achievable in the ion source region, limited the maximum voltage that could be used, and increased the arcing frequency, which is detrimental to stability and long-term operation.

(B. Pressure vessel within a pressure vessel)
Equipment that needs to be sustained at high voltages is typically enclosed in a smooth-shaped high-voltage dome inside an insulating gas-charged pressure vessel to minimize disruptive and potentially damaging arcing events. However, some auxiliary components cannot operate properly in a pressurized environment. Thus, a solution is provided herein in which components that need to be located inside the pressure vessel for reliable operation at high voltages, but cannot operate in a high-pressure environment (e.g., roughing pumps), are installed in a smaller (inner) pressure vessel that is pressurized to nominal atmospheric pressure and connected to the exterior of the larger (outer) pressure vessel via tubing.

For example, as described in the above section, a roughing pump is used to assist a turbomolecular pump that is added to the ion source to remove gas from the extraction region. A roughing pump works best at atmospheric pressure rather than the pressurized environment created by a larger (outer) pressure pump (see, for example, the _SF6 pressure vessel in FIG. 1). Thus, as shown in FIG. 10, a nested pressure vessel configuration is provided in which the roughing pump is located inside an inner (smaller) pressure vessel inside an outer (larger) pressure vessel so that it can operate at a different pressure (e.g., atmospheric pressure). It is noted that in studies conducted during the development of embodiments of the present disclosure, attempts to operate the roughing pump in a pressurized environment led to gas leaking into the pump, so the pump had to run more vigorously. Also, if a roughing pump is not used in the inner pressure vessel, this can lead to gas backflowing through the turbomolecular pump and contaminating the vacuum system.

(CV belt)
Power for components held at high voltages must be supplied in a manner that is electrically isolated from ground. Conventional techniques for providing this energy include isolating transformers and generators driven by insulated shafts or belts. Most belts produced for power transmission applications have either steel cables embedded within them, large amounts of carbon added to the polymer, or both. Both of these features prevent them from maintaining voltage isolation requirements because they make the belts effective electrical conductors. Other belts do not readily conduct electricity, but they are usually either too weak to handle large amounts of transmitted power, or have been observed to become more conductive over time, leading to belt destruction and failure.

A solution to this problem is provided herein by providing a system comprising: a) at least one high voltage component held at a high voltage in an accelerator system that generates a high energy ion beam; and b) a power component electrically coupled to the at least one high voltage component, providing power to the at least one high voltage component (e.g., in a manner that is electrically isolated from ground), the power component comprising a V-belt, the V-belt comprising a plurality of sections (e.g., 3...25...100...400 sections), and which is i) a poor electrical conductor or ii) a non-electrical conductor.

V-belts have been identified that can both handle the power load being transmitted and maintain the necessary electrical isolation. For example, segmented V-belts such as the Fenner Power TWIST have been found to successfully transmit large amounts of power across the voltage gap.

III. High Voltage Systems
In various embodiments, the high voltage system has several improvements that contribute to its improved behavior. These include direct ion implantation, active cooling water resistors, an ideal electrostatic lens design process, and the use of precision insulating balls for electrical isolation and alignment of electronic suppression elements. Each of these improvements will be discussed in turn.

A. Direct Ion Implantation
Many beamlines require components located between the ion source and the accelerator. This low energy beam transport (LEBT) section accepts the beam as it exits the plasma source and delivers it to the accelerator with the required beam parameters. Typically, the LEBT includes, but is not limited to, an analyzing magnet, focusing elements, electron suppression elements, and a beam chopper. Such components are necessary when the beam extracted from the plasma source is not of high enough quality to be accepted by the accelerator. Such LEBT components increase the size, cost, and complexity of the system. The increased complexity generally leads to a less reliable and less robust system. In addition, due to the increased space charge in the beam, these problems are generally more pronounced for high current DC beamlines.

In light of these possible problems with LEBT components, in some embodiments, a direct ion implantation system is provided herein that does not employ any LEBT components. To provide only direct ion implantation, various solutions are employed, including rapidly modulating microwave power, modifying the drift length (the distance between the ion source and the entrance to the accelerator column), reducing the pressure in the accelerator column, and reducing the pressure in the high voltage area (e.g., using the first and second vacuum pumps described above and herein).

The high atomic fraction characteristic of microwave ion sources can eliminate the need for a species analysis magnet between the ion source and the accelerator. Sufficient vacuum pumping in the beamline eliminates the need for background ionization and static electron suppression between the ion source and the accelerator. This is further facilitated by adding a pump at the high voltage end of the accelerator as described herein.

Many ion source technologies, such as those based on filaments, rely on thermal processes and are relatively slow to turn on and off. With such sources, the extraction or acceleration high voltage power supplies must be shunted or switched to rapidly modulate the beam. This adds complexity and cost while generally reducing reliability.

In one embodiment, the microwave ion source is rapidly directly modulated by controlling the driving microwave power. This allows the beam to be rapidly pulsed or extinguished while the extraction and acceleration high voltage power supplies remain steady. Such functionality allows for system commissioning and machine protection without the need for beam choppers, kickers, or high voltage switching circuits. Figure 11 shows an example of a pulsed beam from a modulating magnetron (measured with a Faraday cup) modulating the microwaves incident on the plasma chamber.

In the direct injection architecture, the beam extracted from the ion source is instantly incident on the accelerator, as shown in 12A. This geometry minimizes the drift length and therefore reduces the increase in beam diameter due to space charge. The ion beam diameter is an important factor for the solenoid focusing element. The ability to control the beam diameter and divergence by modifying the drift length between the ion source and the accelerator therefore allows for better performance when designing the entire beamline by matching the ion source, accelerator, focusing elements, and target. Therefore, in an embodiment, the drift length is modified (lengthened or shortened) to optimize the direct injection architecture.

The "drift length" is the physical distance the beam travels in the absence of external electromagnetic fields. This corresponds to the physical distance between the extraction/suppression/extraction lens group in the main system diagram and the entrance to the accelerator column. This is the same location where the LEBT would be used in a non-direct injection system.

Examples of drift lengths before the accelerator are shown in Figure 12B from 20 to 500 mm.

In the field-free drift region, the beam is largely neutralized by background free electrons and space charge effects are significantly reduced. Under these conditions, the envelope of the beam extracted from the ion source can be approximated as a cone with a constant apex angle. The diameter of the beam entering the accelerator at the end of the drift region can therefore be determined by the length of the drift region together with this expansion angle.

Spherical aberration and space charge effects in the accelerator depend on the beam diameter, making the length of the drift region between the ion source and the accelerator an important factor in the system's performance.

Note that to operate reliably, direct injection systems generally require a more finely tuned ion source, which typically requires a lengthy commissioning process by a skilled operator. As described herein, automatic system tuning algorithms increase the speed and reliability of such processes. Any failures can also generally be handled automatically, without operator intervention, by the automatic recovery system described herein. This can effectively minimize or eliminate any damage or downtime caused by such transient events.

The elimination of electron suppression components between the ion source and the accelerator column generally allows any electrons generated in the accelerator, due to interactions with background neutrons or the accelerator walls, to be transported back into the ion source at high energies. This can result in damage to the ion source components, shortening their lifespan, and placing unnecessary loads on high voltage power supplies, increasing their cost.

In a fully optimized system, there will be a negligible level of beam current impinging on any accelerator surface. The majority of harmful backflow electrons are therefore generated by interactions with background neutrons, so reducing the pressure in the accelerator (as discussed above) will minimize these problems. As detailed herein, increasing the vacuum pumping capacity in the high voltage region of a system with an electrostatic suppression lens (described further below) between the ion source and the accelerator has been found to be an effective way to improve system reliability and stability while reducing the background pressure and therefore reducing backflow electron flow. Adding a similar pump to the high voltage end of a direct injection system should, in some embodiments, further improve overall stability and increase the life of accelerator components. The adverse effects of backflow electrons reacting to the ion source can be further mitigated using a so-called reverse waveguide, discussed in detail herein.

Implementing direct ion implantation, such as by using the techniques discussed above, can reduce beam diameter and improve beam transport for high current ion beams. Tuning the beam characteristics can allow for smaller apertures on the differential pumping system, longer beam transport distances, or better acceptance into downstream high energy accelerators. In general, smaller beam sizes and apertures are important for gas targets. Longer transport is also important for targets that need to be located at large distances from the ion source, including but not limited to accelerator driven subcritical assemblies. Acceptance into downstream accelerators is also important for high energy physics laboratories.

(B. Active cooling water resistor)
High voltage power supplies (HVPS) are used to power the accelerator system components. When testing such an HVPS, the output is connected to a test load to ensure that the HVPS meets specifications. The test load must withstand a maximum of 300 kV DC and dissipate a maximum of 30 kW, or about 3 kW, or about 5 kW of heat. Constructing such a test load is a feasible solution for testing the load at different loads. Requires the purchase of multiple expensive specialty resistors in order to operate.

Some accelerators also use resistor dividers, consisting of a series of resistors, to divide the voltage evenly along the accelerator, preventing arcing and providing a uniform electric field to properly accelerate the ion beam. Conventional resistors are rated for high voltages, are bulky, and have limited power dissipation, which limits the accelerator's performance.

In one embodiment, provided herein is a recirculating high power high voltage water resistor or test load that has been used to test HVPS at voltages up to 300 kV and power levels up to 30 kW. The same concept is also used as a flexible high voltage grade resistor for electrostatic accelerators (see FIG. 13).

These systems and methods use recirculating conductivity controlled water as the resistive element. Insulated tubing (e.g., plastic tubing) is connected between the ground electrode and the high voltage electrode. A water pump takes water from a reservoir and circulates it through the electrodes and through a heat exchanger to remove dissipated heat and return it to the reservoir.

Deionizing (DI) resins are used to reduce the conductivity of the water, and dilute metal salt solutions are used to increase the conductivity as needed. By actively controlling the conductivity of the water, the resistance can be varied over a wide range. The DI resins used are generally capable of producing deionized water with resistivities of 15 Megaohm-cm or higher. The resins are often commercially provided as "mixed bed" resins, consisting of equal amounts of a strong acid cation resin in the hydrogen form and a strong base anion resin in the hydroxide form.

The voltage rating of the water resistor can be changed by adjusting the length of the insulating tubing to increase or decrease the breakdown voltage as desired. The power capacity of the resistor is adjusted by selecting the tubing diameter and water flow rate so that the water does not exceed its boiling point at the design power rating.

During development of embodiments of the present disclosure, it was found that soft vinyl tubing developed pinhole leaks due to high voltage arcing. Suitable materials for non-conductive tubing include, but are not limited to, polycarbonate, polymethyl methacrylate (PMMA), and polyethylene. Metal salts that may be used include, but are not limited to, copper sulfate, sodium chloride, ammonium chloride, magnesium sulfate, sodium thiosulfate.

Exemplary embodiments of these systems are as follows: The water resistor is initially filled with deionized water. For this reason, the materials used in the construction of the water resistor should be compatible with the DI water system. Generally, for best performance, all metals in the system should be the same, which could be, for example, copper, aluminum, or stainless steel. Mixing metal types generally increases corrosion and shortens the life of the components. The metal salt used to reduce the resistance should be compatible with the metals selected, for example, copper sulfate is used with copper, ammonium chloride is used with stainless, etc. A 15 or 18 MΩ-cm mixed bed DI resin is used to remove excess ions from the solution and increase the resistance. In one embodiment, the following is employed: stainless electrodes, stainless heat exchanger, magnesium sulfate salt, and 15 MΩ-cm color changing DI resin.

In an exemplary application running for high power, high voltage loads, the system was as follows: The insulating tubing was two lengths of polycarbonate tubing with an inside diameter of 0.95 cm and a length of 90.0 cm. The DI resin was ResinTech MBD-30 indicator resin. Copper tubing was used to make the electrical connections to the dilute salt water. The electrolyte was copper sulfate.

The resistance of the test load was calculated as R=rho ^* L/A, where rho is the resistivity, L is the tube length, and A is the tube area. Using pure DI water with 18 megohm-cm resistivity, the test load resistance was R=18e6 ohm-cm ^* 2 ^* 90cm/0.71 sq. cm.=4.6e9 ohms. This high resistance was essentially zero load, allowing a full voltage zero load test to be performed.

Copper sulfate was then added to reduce the resistivity to 2960 ohm-cm, which resulted in a resistance of 750 kilohms. This allowed the test load to be operated at 150 kV, 200 mA. 30 kW of power was dissipated to cool the water through a heat exchanger.

In some embodiments, the PLC/software control will fully automate the system, allowing the operator to select the resistance, and the system will automatically compensate for slight drifts in temperature or conductivity. Additionally, a sealed system or other method to prevent atmospheric oxygen or _CO2 from contacting the water will increase chemical stability and extend the life of the system by requiring fewer consumables or increasing the time between service intervals.

(C. Lens Design)
An electrostatic lens stack is used to extract ions from a microwave plasma source and form them into a beam. The electrostatic lens stack consists of i) a plasma lens, ii) an extraction lens, iii) a suppression lens, and iv) an exit lens. The precise shapes of the lenses affect the beam performance at given source parameters and applied voltages in terms of current density, spot size, divergence, and emittance. These affect the system robustness, total extraction current, and high voltage requirements. This is required to determine the appropriate lenses to obtain a beam of desired properties as the process propagates through downstream components (e.g., accelerator columns, focusing solenoids, or low conductance apertures) that are subject to operational constraints such as maximum applied voltage and electric field.

In one embodiment, a lens design process is provided herein that begins with an internal computer code that determines a nominally ideal profile for the plasma and extraction lens, given the desired beam properties. This also generates files and inputs the calculated lens geometry into PBGUNS (Particle Beam GUN Simulation), a commercially available program used to stimulate ion beam transport through the extraction system and downstream components. Figure 14 shows an exemplary user interface for the lens design software application.

PBGUNS outputs beam trajectories and results that can be used to verify the suitability of the lens stack being designed or suggest modifications that can be made to the geometry to optimize beam quality and therefore overall system performance. Figure 15 shows a sample beam trajectory plot from PBGUNS.

The inputs to the lens shape determination code are the beam current, extraction voltage, ion species ratio, maximum electric field, and ion current density at the plasma lens aperture. The code outputs a lens that satisfies the equation for zero charge outside the beam (Laplace's equation) and results in a spherically converging space-charge limited ion flow between the plasma and the extraction lens while producing a congruent solution between the two regions at the edge of the beam.

PBGUNS has many inputs beyond the system geometry. These include the grid accuracy, empirically determined beam neutralization factors, and electron and ion temperatures in the source plasma. The program outputs beam trajectory plots, as well as phase space plots and emittance calculations at specific axial locations. Some limited beamlet data is also output for a single axial location per run, which can be used to post-process the results in more detail.

In some embodiments, other programs are used to design lenses that allow 3D configurations to be simulated (e.g., when considering a multi-aperture extraction system to increase the total current that can be extracted from the plasma source, which may be important for some applications). Other software packages such as IBSIMU also allow 3D configurations while also running 2D geometries faster than PBGUNS, but the full calculations may not be as accurate.

D. Implementation of Suppression Elements High energy ion beam generators may employ an extraction lens stack negatively biased with respect to the extraction lens, with a suppression electrode located directly downstream from it, followed by an exit electrode in electrical contact with the extraction lens. The resulting drop in electrostatic potential prevents electrons created downstream (e.g., by ionization or secondary electron emission from a solid surface) from accelerating to high energies and damaging source components. The trapped electrons may also contribute more effectively to space charge compensation of the ion beam, reducing beam size, divergence, and emittance. Such a lens stack may therefore promote system reliability, improve beam quality, and increase the total current that can be delivered to the target, resulting in additional uptime and throughput.

Provided herein are components used to align and hold together electrodes in a lens stack while withstanding high voltages between them. The mechanism is mechanically robust, provides electrical insulation, is ultra-high vacuum compatible, rated for high temperatures, and is a complex set of criteria to balance.

In some embodiments, an insulating ball (e.g., a ceramic ball) is pressed between the conical depressions on each pair of electrodes stacked together, as shown, for example, in FIG. 16. In some embodiments, for each lens gap, three insulating balls (e.g., ceramic balls) are evenly spaced in azimuth coordinates to achieve mechanical contact on a perfectly defined plane. Given their high degree of spherical symmetry and diameter tolerances, the ceramic balls allow for self-alignment of the lens, since the two electrodes that are tightly pressed against the opposite sides of the three ceramic balls have no residual degrees of freedom compared to other geometries.

Ceramic balls are rated for ultra-high vacuum, very high temperatures, are very hard and rigid, have high dielectric strength, and provide insulation for use at high voltages. In some embodiments, the entire lens stack is held by metal bolts between the extraction and ejection electrodes since they are held at the same electrostatic potential and electrical contact between them is desired. Metal bolts are also much more durable than ceramic bolts.

Ceramic balls are easily manufactured or available as off-the-shelf components at relatively low cost with very high precision of diameter (about 0.1%) and sphericity (about 0.01%). Ceramic balls are often made mostly from alumina and are rated for temperatures in excess of 1,000°C, although other materials may be used.

Prior to the use of precision ceramic balls, ceramic bolts, nuts, and washers were used. These can be rated for vacuum, high temperature, and high voltage operation. However, they are subject to shear stresses and can easily break, especially when the axis of the lens stack is oriented horizontally. Also, because the through holes in the electrodes are necessarily larger than the outer diameter of the bolt threads, the lenses have a minimum of two degrees of freedom so that self-alignment is not a feature of that type of assembly.

The use of precision ceramic balls allows for a mechanically robust assembly of the extraction lens stack using suppression electrodes, adding inherent self-alignment between the lenses while enabling use at high voltages, high temperatures, and ultra-high vacuum. This component increases the total current that can be reliably transported to the target while helping to improve overall system reliability in terms of mechanical stability, beam quality, and protection of the source and beamline components.

(IV. Neutron generation target)
Several advances have been made to neutron producing target systems that contribute to their exemplary performance. These include A) active cooling for solid targets, B) argon sputter cleaning process, C) gaseous targets. D) Reverse gas injection; and E) implementation of a beam scraper.

(A. High power density solid target cooling)
For accelerator-driven neutron generator systems, the majority of the ion beam energy results in target heating rather than nuclear reactions. High yield systems necessarily require high power ion beams and the resulting large neutrons generated at the target. Requires removal of heat load.

A solid target consists of a reactive species, typically deuterium or tritium, embedded in a solid matrix of non-reactive material. Such a non-reactive matrix would generally further reduce the efficiency of the generator, since any interaction with the ion beam would result only in waste heat and not any desired nuclear reaction. In addition, the high density of a solid target generally leads to a short stopping distance for the incident ion beam, resulting in a high volumetric power density being deposited into the target.

The volume in which the desired neutrons are produced through the fusion reaction is defined by the volume within the target in which the beam ions are deposited. For certain applications, including but not limited to fast neutron radiography, a point neutron source is desirable to provide higher quality images. This corresponds to a small ion beam spot size on the target.

For a given total neutron yield, measured by the number of neutrons produced in a period of time, the neutron flux, measured by the number of neutrons per time per area, generally increases as the neutron production volume within the target is reduced. High neutron flux is desirable for applications including, but not limited to, neutron activation analysis and materials testing for nuclear reactor components.

For reasons including but not limited to those described above, depositing the energy of the ion beam into a small volume is desirable for the performance of accelerator-driven neutron generators. Beam focusing elements can be used to reduce the spot size on the target to an almost arbitrarily small area limited by space charge effects. In practice, the achievable spot size is limited by the high power deposition of the ion beam into a solid target.

For applications of accelerator-driven neutron production via fusion reactions between nuclei of hydrogen isotopes, a solid target material with high hydrogen storage capacity, such as titanium, is desirable for high neutron yields. Deuterium or tritium is implanted directly into the target by the beam, either in situ or in an oven-baking process.

Besides physical destruction of the solid target through mechanisms including melting and ablation, solid target neutron generators utilizing deuterium or tritium nuclear reactions must be maintained below a temperature at which diffusion would lead to loss of hydrogen from within the target material. In general, the hydrogen vapor pressure of metal hydrides is very high at temperatures above about 250 degrees Celsius.

In general, there are two fundamental cooling requirements for ion beam targets. First, the total average power deposited by the beam should be removed to prevent bulk heating of the target assembly over a time series of approximately the thermal time constant. Second, the instantaneous power density of the beam incident on the target material should be low enough to prevent immediate localized material damage.

The average ion beam power is determined by the product of the beam current, beam energy, and duty cycle. This value is typically on the order of several thousand to tens of thousands of watts in some of the exemplary systems described herein, although the same principles apply to higher power levels. The resulting steady-state bulk temperature rise is determined by the mass flow rate and specific heat of the coolant. This first requirement is easily met with moderate mass flow rates of coolants (e.g., 10-100 gallons/min of coolant), including but not limited to water, glycol, or oil.

The second requirement, volumetric power density, is generally more difficult to achieve for high performance systems. The incident beam power is deposited into a narrow surface volume defined by the beam spot size and the stopping power of the beam in the target. This power must be transferred through the target material into the coolant before being removed. Heat transfer at the interface is defined, in part, by the materials, geometry, surface conditions, and coolant fluid dynamics.

The target temperature should be kept below about 250 degrees Celsius to prevent loss of embedded hydrogen and hydrides, which are required for the fusion reaction. This is accomplished using minimized target wall thickness, high thermal conductivity materials, increased coolant surface area, turbulent coolant flow, and clean coolant channel surfaces.

The performance of early systems using open-loop water cooling was found to degrade over time. Given the very low thermal conductivity of the mineral deposits that accumulate within the cooling channels, even extremely thin layers have a significant effect on heat transfer and the resulting target surface temperature. The high temperatures inherent at the target tend to increase the precipitation of mineral deposits, which can restrict coolant flow, reduce cooling capacity, and create a runaway failure mode.

Closed-loop cooling with actively filtered and deionized coolant prevents such deposits within the target while extending the life and improving the target's performance.

One approach to reducing the power density on a solid target is to position it at an oblique angle so that the ion beam is deposited over an ellipse with high eccentricity and increased surface area. Many targets have been tested that utilize a single oblique plane, an array of oblique planes, or a cone. Such geometries are used on high power beam stops where neutron production is not the primary application. Targets using this method are necessarily larger, more expensive and complex, and generally require more auxiliary hardware. This makes such an approach undesirable for systems requiring a point neutron source or for compact, easily portable systems.

To reduce the target size, the beam spot size on the target must be reduced, resulting in higher power density. To maintain the target surface temperature requirements under these conditions, more efficient heat transfer is required. In some embodiments, the target walls are of a minimum thickness (e.g., 0.005-0.020 inches, e.g., 0.010 inches). This dimension is limited by the structural integrity required to contain the coolant channel pressure. The temperature difference between the target surface and the coolant that intercepts the beam's power is proportional to the target wall thickness and the thermal conductivity of the wall material. Thus, both the material and physical structure of the target and cooling channel walls determine the performance of the solid target. Reducing the target wall thickness therefore allows for lower target surface temperatures. An ideal wall material has high thermal conductivity, high tensile strength, and high machinability. Such materials include, but are not limited to, copper, silver, gold, diamond, diamond-like carbon, or combinations thereof.

Additionally, the effective surface area is increased through the addition of fins, ribs, or other convolutions. Such features can increase the structural strength of the target allowing for thinner walls. The features can be manufactured using multiple techniques, including but not limited to milling, casting, or additive manufacturing. Examples of turbulence-inducing structures include multiple parallel fins with recessed holes to interrupt a smooth surface. An example structure is shown in FIG. 17.

In some embodiments, water is used as the coolant. This allows for the use of a wide range of low-cost, reliable commercial pumps, filters, and other auxiliary equipment to support the cooling system.

Other embodiments may utilize other coolants, including but not limited to oil, gas, or liquid metal. Additives may be used to modify the properties of the coolant.

A high quality closed loop coolant system maintains clean coolant channel surfaces. This sealed system prevents atmospheric oxygen or other substances from being available to react with the surfaces of the coolant channels. The coolant loop is also further processed using techniques including, but not limited to, deionization and filtration.

Laminar flow creates an insulating layer at the fluid-solid interface of the cooling channel, limiting heat transfer. Irregular features such as the intermittent dimples and spiral indentations illustrated in FIG. 18 tend to induce turbulence, which in turn improves the heat transfer of the system. The fluid coolant channels are located in the face of the solid target assembly. This assembly is located at the end of the beamline. In some embodiments, the solid target is at ground potential and does not require any special connections to the overall system. In some embodiments, the solid target is thermally isolated from the rest of the system. This allows calorimetric measurement of the power deposited by the ion beam into the target by monitoring the temperature and flow rate of the coolant through the target. Since the energy of the ion beam is known, the deposited power can be used to determine the current delivered to the target by the ion beam.

Another embodiment of the solid target assembly is electrically isolated from the overall system, allowing it to be biased to a high voltage to increase the effective ion beam energy and neutron yield. Such an embodiment involves the use of a fully closed loop cooling system in which coolant is delivered to the high voltage solid target from a pump located at ground potential or isolated at high voltage. Such methods are similar to those described herein for providing cooling or power to an ion source, which is also electrically biased to a high voltage with respect to ground.

Turbulent flow also generally has a higher pressure loss. Coolant flow rate and pressure drop should be considered in the design of turbulence-inducing features. Computational fluid dynamics simulations are used to determine these values and match them to the performance of the coolant pump system. By adjusting the number of parallel and series elements, the target operating flow rate and pressure drop are adjusted.

The heat transfer performance of a target is characterized by the temperature difference between the coolant and the target surface. The absolute temperature of the surface is therefore reduced for a given system by reducing the inlet coolant temperature. Closed-loop coolant pre-cooling is achieved using a chiller or other methods. The minimum achievable coolant temperature is generally limited by the melting point of the coolant.

Pre-cooling of aqueous coolants is limited by their relatively high melting point. The use of other coolants, such as helium, allows for much lower temperatures as the coolant enters the target. This results in lower target surface temperatures for a given ion beam power density. Similarly, higher ion beam power densities, resulting in more point-like neutron sources and higher flux, can be achieved while maintaining the required low target surface temperatures.

The low mass of the hydrogen species results in a low sputtering rate of the metal target. The lifetime of the target surface is shortened if the beam contains heavier ion contaminants that can be removed using an analytical magnet or other mass filtering components in the beamline prior to the target.

High power density ion beam targets allow for more physically compact and portable systems, more point neutron sources, and higher neutron fluxes.

B. Purifying Solid Targets to Maintain Neutron Yield
Neutron sources sometimes use beam targets plated with titanium metal. Titanium adsorbs significant amounts of deuterium so that the incoming deuterium can cause a fusion reaction and release neutrons. However, titanium is an extremely reactive metal that can also react with oxygen and nitrogen, forming a barrier to the deuterium beam and reducing neutron output. Trace contaminants in the vacuum system can be high enough to create this problem.

In some embodiments, a small amount of argon gas (e.g., 1-10 cubic centimeters per minute) is flowed into the vacuum system while the beam is operating. The ion beam transfers some kinetic energy to the argon gas. Energetic argon atoms then impact the target surface and remove the contaminating oxide/nitride layer by sputtering. While argon is much heavier than the primary beam species and therefore efficient for inducing sputtering, its chemical inertness prevents it from forming titanium and other compounds on the target surface. Figure 19 shows the effect of titanium compound formation and the argon purge process on neutron yield. The target initially loads with deuterium for up to 10,000 seconds, but then a slow buildup of titanium oxide/nitride reduces the neutron output. A short argon purge occurs at 125,000 seconds and a long purge occurs at 150,000-175,000 seconds to return the neutron output to the initial level.

Argon should be delivered into the vacuum system as close to the solid target as possible to make the local argon pressure near the target as high as possible without excessively increasing the overall vacuum system pressure. In some embodiments, an argon gas source resides inside the vacuum and is connected to the vacuum system by a metal tube that delivers argon directly at the solid target location.

Other heavy inert gases such as krypton and xenon can also be employed, but they are prohibitively expensive.

The only previous method was to remove the target from the system and mechanically clean the target to remove the titanium oxide/nitride layer. This was a time consuming process that removed significantly more of the target plating than was necessary, greatly shortening the target life. Furthermore, the periodic replacement of the target reduced the system's uptime and therefore the total throughput for the user over time.

C. Tube Opening
In gaseous target neutron generators, a large pressure gradient needs to be maintained between the target and the accelerator to maximize the total neutron yield. The aperture separating the target gas from the ion beam accelerator is therefore necessarily small (e.g., a few millimeters in diameter). The ion beam power density, when passing through the aperture, is correspondingly large (hundreds of MW/ ^m2 ) and cannot be tolerated by any solid surface in steady-state operation. Small deviations in beam focusing and steering due to thermal/mechanical or electrical fluctuations in the accelerator system can result in severe damage to the target entrance aperture. This can lead to degradation of system performance if the pressure gradient cannot be maintained, or even severe system damage due to loss of vacuum and/or cooling water entering the vacuum system.

Ion beams are several centimeters in diameter when they leave the acceleration stage and must be focused to a few millimeters to pass through an entrance aperture to the gaseous target. The axial distance to which the beam is focused to its minimum diameter depends on the current in the focusing solenoid. A variety of adjustable focusing mechanisms may also be used, including electrostatic or magnetic quadrupole multiplets or permanent magnet/electromagnet hybrids.

In some embodiments, the ion beam is laterally deflected in two orthogonal directions by varying the current in a pair of crossed dipole electromagnets ("steering" magnets) so that the central axis of the beam is centered over the gas target aperture, compensating for the accumulation of angular deviations due to mechanical tolerances in the alignment of beamline components over the long beam transport distance between the plasma source and the gaseous target.

Provided herein is a system for sensing the distribution of ion beam power over a target aperture and using the information to actively control the focusing and steering of the ion beam through the aperture. In some embodiments, this is accomplished with four-quadrant thermal instrumentation embedded near the upstream-facing surface of the gaseous target aperture, equally spaced at 90 degree intervals around the axis of the aperture. An exemplary implementation uses copper constantan thermocouples in a copper target aperture, which may also serve as the copper legs of each thermocouple, or copper wires may be separately led out. Other embodiments use platinum resistance temperature detectors (RTDs), thermistors, or semiconductor temperature sensors.

The four quadrant temperature signals are summed to provide an average target aperture temperature, which is used to maintain ion beam focusing. Adjusting the current in the focusing solenoid and minimizing the target aperture temperature maintains the best focusing against small perturbations due to beam voltage or current fluctuations, or due to overall beamline deflection or distortion due to thermal expansion or mechanical stresses.

In this implementation, the sensors are arranged around the axis of the beam passing through the target aperture at the location towards which the steering dipole magnet deflects the beam laterally. The temperature difference between the first pair of diametrically opposed temperature sensors is used to maintain beam alignment between the two sensors in the pair, which is also the center of the gas target aperture. Thus, the current in the first magnet can be varied to minimize the temperature difference between the first pair of sensors, which corresponds to the direction in which the magnet deflects the ion beam. The difference between the second pair of diametrically opposed sensors, and the corresponding variation of the current in the second steering dipole magnet, can be used to center the beam in a direction orthogonal to the first pair of sensors. Figure 20 shows an exemplary embodiment of the system. The top panel shows the location of the thermocouple measurement points on the target aperture. The bottom panel shows the components in relation to the beam and the dipole steering magnet.

D. Reverse Gas Injection
In a gaseous target neutron generator, the pressure in the target should be as high as possible so that the beam stops completely at the smallest possible distance and the pressure just before the target should be as low as possible so that energy is not wasted and the neutrons are produced in an area where they cannot be used effectively.

Components are provided herein for increasing the pressure differential across the final opening. In particular, a reverse gas jet is provided herein for creating an increased pressure differential across the final opening. An exemplary configuration of a reverse gas jet is shown in FIG. 21.

Modeling was done using a computational fluid dynamics (CFD) program to generate nozzle geometries that would increase the pressure differential across the target aperture. Initial trials used nozzles that did not diverge after converging, which did not work at all at the pressures of interest. Aspects such as narrowing gap, nozzle angle, nozzle length, and pressure in the plenum were varied. Plenum pressure was always kept below atmospheric pressure so that gas leakage and gas retention were kept to a minimum. After significant effort, a configuration as shown in FIG. 21 was developed that provided the desired pressure differential.

The aperture around which the gas jet nozzle sits was chosen to be 3/8 inch (although other dimensions could be used) based on other considerations such as the size of the beam as it passes through the aperture. With this aperture diameter and the type of pump desired to be used to drive the gas jet, a narrowing gap of less than 0.01 inch was sufficient to keep the pressure drop high enough to induce supersonic flow. A mean nozzle angle of 12.5 degrees was found to be optimal using parametric studies.

(E. Beam scraper)
In some systems, a mechanism for inserting a solid target into the path of the beam, which can block arbitrary portions of the beam, is sometimes desirable to precisely control the total current delivered to the target. Such beam scrapers can also be used to determine the beam profile, which is useful information during optimization of the overall system.

In some embodiments, a solid target is attached to a rail feature and moved along the rail by a linear actuator consisting of a long screw driven by a motor. The software measures the target's position along the rail in real time using "home" and "limit" switches and adjusts the position based on feedback from the system.

Early approaches used rotary feedthroughs with threads inside the vacuum. However, this required difficult lubricant selection, preventing wear in the vacuum, as well as coupling multiple shafts together in tight quarters. Additionally, the vacuum chambers were much larger and more expensive.

An alternative approach has also been attempted with success. The motors for the linear actuators are mounted outside the vacuum vessel, generating heat and using air for cooling. This required the use of linear vacuum feedthroughs. Because most linear motion vacuum feedthroughs are bellows sealed, they require forces to balance the vacuum forces applied to the bellows, thus putting more strain on the motor to overcome these forces. Bellows sealed feedthroughs also have a limited number of compression cycles that they can withstand before failing. For these reasons, magnetically coupled feedthroughs are more desirable, as they do not have any of these problems.

Also, due to the negative consequences of water leaks in vacuum systems, in some embodiments, all-metal hoses and fittings are used and brazing is used to manufacture the entire target. This ensures that leaks are not possible without the metal itself failing. The target should also be designed so that no parts of the target, including rails, support structures, or tubing, are in the path of the beam when fully retracted.

Figure 22 provides an example configuration of a beam scraper. The motor and magnetic coupling are shown outside the vacuum boundary. The target and associated water hose are shown inside the vacuum boundary. Solid targets are used on beams smaller than 6 inches in diameter. When fully retracted, the part closest to the beam is usually the face of the target that is struck by the beam when extended, and its edge is more than 3 inches away from the centerline of the beam.

An alternative embodiment involves mounting a solid target on a hinge so that it is redirected towards the beam path instead of translating linearly. This approach reduces the power density on the target until fully closed, reduces space requirements, and allows for simpler and less expensive feedthrough designs. As a tradeoff, tubing may be more difficult to implement for this configuration. This approach allows for a normal close/open configuration and is considered to have faster close/open times.

An alternative to systems requiring an axially symmetric beam to reach the primary target involves an iris type beam scraper.

(V. Automatic Control Systems)
In some embodiments, the systems and methods employ one or more automatic control components, including, but not limited to, optical fiber interlocks, health monitoring systems, and automatic recovery systems after arcing events, as well as closed loop controls to manage beam stability.

(A. Optical Fiber Interlock)
High energy ion beam generators incorporate one or more, typically several, high voltage sources. For safety reasons, the user/controller station should be electrically isolated from the rest of the device/system, and furthermore, components should exist to connect the user station to the interlock system of the other parts of the device/system.
This creates a significant conflict between safety and operability: approaches such as the use of isolation transformers to provide electrical isolation between the two subsystems are not technically or economically practical due to the presence of voltages up to tens of thousands of volts.

The interlock may consist of several normally closed switches in series that must remain closed to indicate that one piece of equipment is safe to operate, or several normally open switches in parallel that must remain open to indicate that one piece of equipment is safe to operate, or both series and parallel loops.

In some embodiments, the conflict between safety and operability is resolved by employing a fiber optic connection between the device's interlock system and the user station's interlock. This provides the required electrical isolation. To provide a robust connection that is not susceptible to accidental bypass, in some embodiments a frequency generator is included within the fiber optic interlock, as detailed below. In some embodiments, a multiple signal verification procedure is also implemented to protect the system from single points of failure producing false closure results.

The first attempt to address the problem involved a fiber optic transmitter that generated a light when a user station interlock was closed. This method was unsatisfactory because the user station interlock closed signal did not depend on any earlier components in the interlock train and therefore did not properly contain the user station.

To solve the problems with the first implementation, a bidirectional link was provided. When the upstream interlock switch is closed, light is transmitted through the fiber optic cable to the user station. The light is converted to a voltage signal that passes through the interlock switch at the user station. Once there is a light signal from the device and the user station switches are all in the "safe" position, the light is transmitted back to the device, thus closing the interlock loop. The problem presented by this solution was that it was simple to bypass the user station interlock device by simply connecting the transmitter and receiver on the device, thus closing the loop regardless of the state of the interlock switch in the user station.

The fiber optic interlock signal has been made frequency dependent to make it more difficult to circumvent the interlock system. A small frequency generator triggers the fiber optic transmitter, causing the light to pulse at a set frequency. The receiver is configured to be sensitive to the frequency of the light pulse it is detecting, and if the proper frequency is not present, the receiver will not indicate that the interlock is secure.

Furthermore, to allow a single device to utilize multiple fiber optic interlocks, a printed circuit board (PCB) was constructed so that, with the appropriate tooling, any one of four different frequencies could be selected. This also allows a single bidirectional link to use a different frequency for transmission than that used for reception, thus reserving any obstacles in the way of bypassing the integrity of the interlock signal.

Figure 23 shows an example block diagram of a fiber optic interlock system that may be employed with the system. Fiber optic transmission occurs between the transmitter and receiver through electrically isolated portions of the interlock circuit. The transmitter may employ an input from a standard copper interlock. This can accommodate a single loop with N/O (normally open) or N/C (normally closed) switches, or a double loop with one of each type. When all interlock switches are in the correct position, a voltage reference exists. When the voltage reference exists, the voltage is scaled to a selectable level. A frequency converter generates a frequency proportional to the scaled voltage. A fiber optic driver pulses the fiber optic output to the user station at the selected frequency.

At the receiving end, a fiber optic receiver converts the fiber optic pulses to a voltage square wave of the same frequency. In some embodiments, a frequency-to-voltage converter takes the frequency received through the fiber optic transmission and converts it back to the original reference voltage. A window comparator verifies that the proper frequency is being received. When the comparator verifies that the received frequency is correct, a driver circuit closes a pair of N/O contacts and opens a pair of N/C contacts for integration into one or more local wiring interlock loops. An output is provided to a local interlock train that can accommodate an N/C loop, an N/O loop, or both. In some embodiments, a missing pulse detector circuit provides a secondary source of detection when a pulse train is missing from the fiber optic signal. When the rising and falling edges are independently verified to be present at the expected intervals, a driver circuit closes a pair of N/O contacts and opens a pair of N/C contacts for integration into a local wiring interlock circuit. An output is provided to a local interlock train that can accommodate an N/C loop, an N/O loop, or both. In some embodiments, a second frequency-to-voltage converter takes the frequency received through the fiber optic transmission and converts it back to the original reference voltage. A buffer stage then sends an analog signal to the controller to be used as software verification that the correct frequency transmission is being received. This component increases system safety to a desired level while remaining technically and economically practical.

(B. Health Monitoring) Considering the high power carried by the beam, it is important to ensure that it does not cause thermal damage to the system's components. Damage can be caused by the beam interacting with the system components in non-normal situations. Specific material selection and cooling mechanisms are implemented for components that may interact with the beam so that different protection schemes are implemented depending on the energy density that may be deposited on each component.

In some embodiments, instrumentation and multiple sensors are integrated into the system to measure temperature and cooling water flow rates. These measurements allow for monitoring the amount of power being deposited on the various cooled system components. A combination of minimum flow rate, maximum temperature, and maximum power thresholds allows for protection of the system hardware. These values are continuously monitored by sensors covering all components that may be damaged by interaction with the beam. In some embodiments, each sensor has a configurable level above or below which an alarm is activated, triggering automatic control system action to intervene and ensure safe operation and minimize or prevent damage.

In some embodiments, sensors for liquid level are integrated into the system to measure the presence of neutron moderator required for safe operation. In some embodiments, a combination of signals from multiple sensors are used together to determine operation within safe parameters, e.g., voltage draw and current, and to determine resistance in the magnetic coils.

In some embodiments, feedback signals from components are monitored to ensure operation within desired safety limits, e.g., power draw on turbomolecular pumps and forced air cooling fans.

In some embodiments, feedback signals from integrated components such as the high voltage power supply, gas flow controller, and magnetron power supply are monitored and their outputs compared to expected set points to determine safe operation.

In some embodiments, integrated components are prevented from being set to unsafe set points by the control algorithm, for example, to prevent a user from commanding a microwave generator when the system is not in a state where microwaves can be safely operated. Another example is to prevent beam operation when no part of the system is in a state to safely transport or accept a beam.

In some embodiments, the health monitoring system has both "alerts" and "alarms." Sensors can be configured to signal an "alert" condition and display a warning indicator to the user if the signal deviates from normal operating values. Deviations of greater magnitude trigger an "alarm," resulting in an automated control system response to the condition. In some embodiments, an "alarm" acts in a latching fashion, requiring the user to reset the condition from the control system to remove the alarm status.

One of the challenges encountered with health monitoring on particle accelerators is to filter out false positives due to short-lived transients that cause unnecessary activation of an alarm. High voltage systems inherently generate electromagnetic pulses (EMPs) and therefore electromagnetic interference (EMI). Sensor and component data, transmitted to the control system using analog voltage signals, can be susceptible to EMI pickup. In some embodiments, the raw signal data is processed to filter out EMI and prevent unnecessary activation. In some embodiments, an alarm is not triggered until the duration of an individual signal is longer than is characteristic for EMI pickup. In one example, a single transient must exceed 75 milliseconds prior to activating the alarm. Additionally, in some embodiments, the system is configured to activate if multiple EMI pickup events occur within a certain period of time. In one example, five transient events within a three second time window are considered an invalid activation of the alarm. In some embodiments, both a single event lasting longer than the characteristic EMI pickup and multiple events occurring within a period of time are analyzed together, such that an alarm is activated when either event occurs. This combination of counting EMI events and tracking them over time, but not activating alarms on individual EMI events, allows for reliable continuous operation.

An automatic response from a control system to an "alarm" can be a safe shutdown or an automatic recovery. A safe shutdown is, for example, when the control system automatically turns off the accelerator and places the components in a safe state. An automatic recovery is, for example, when the control system takes a prescribed course of action to return the system to normal operation.

(C. Automatic Recovery)
Occasional "arc-down" events, where current finds a path from a high voltage point through an undesirable path to ground, are not completely avoidable in high voltage accelerators. Preventing the system from remaining in an undesirable state after an arc-down first required trained users to face the user interface to the control system and be ready to act at all times, which is resource intensive. Recovery from an arc-down required several components to be turned off and then back on in a sequence with fault removal on some components as part of the recovery sequence.

As an extension of the health monitoring system described in Section V(B) above, an "alarm" condition is used to indicate that an arc-down event has occurred. An automatic recovery sequence is then executed to return the system to operation without user intervention, much more quickly than a human user. During extended continuous startup, this feature has increased the effective uptime of the system from approximately 95% to over 98%.

In some embodiments, certain conditions are flagged in the system for automatic recovery while other conditions are flagged for human intervention. Example of automatic recovery from an arc down event on a high voltage power supply (hvps). An hvps arc down event is identified by an under voltage alarm on the hvps and/or the extraction power supply. After detection of a fault condition, an automatic recovery sequence is executed that includes disabling closed loop feedback, disabling the magnetron power supply, clearing the system fault, resetting the hvps, enabling the extraction power supply, enabling the magnetron power supply, and finally re-enabling closed loop control. Any fault that is not identified as having an automatic recovery sequence triggers an automatic shutdown sequence. The automatic shutdown sequence includes disabling each component in a safe sequence. An example of a safe shutdown sequence includes disabling closed loop control, disabling the magnetron power supply, disabling all gas flow controllers and power supplies.

In some embodiments, if the recovery sequence is performed more than a configurable number of times within the time window (e.g., 3 recovery attempts within a 10 second period), the control system performs a graceful shutdown rather than a recovery sequence.

The control system for the accelerator is responsible for monitoring the components at high voltage, the components at ground voltage, and connecting to a user interface for human interaction. In some embodiments, communication between the different locations is carried out over fiber optic connections to maintain electrical isolation. In some embodiments, the main system controller is directly connected to the high voltage and ion source microwave power supplies and can deterministically set these components to a safe state. Because there are multiple locations of components and non-deterministic communication protocols between the locations (Ethernet, TCP/IP), a watchdog architecture is used to monitor connectivity. In the event of loss of connectivity, the system automatically and deterministically transitions to a safe state.

Due to the non-deterministic nature of the communication protocol, some amount of communication loss is expected. From time to time, the watchdog reset may be delayed. In some embodiments, rules are configured based on how often the watchdog checks connectivity and the extent to which the watchdog reset may be delayed. This configurability reduces false positives, where the watchdog communicates a safe state to the system.

D. Closed Loop Control for Beam Stability
Certain applications of neutron generators require the neutron flux output to be maintained within 1% maximum amplitude of the flux set point, a value that varies over approximately 5 orders of magnitude. Open loop control by a skilled operator is insufficient to ensure that the flux output remains within the required accuracy due to the multiple variables that affect the system dynamics.

Closed-loop control of either the High Voltage Power Supply (HVPS) setpoint or the beam scraper position demonstrated improved accuracy of the flux output and the ability to compensate for physical variations such as thermal variations or target loading and signal noise. Control of the HVPS setpoint provides a faster dynamic response in the measured flux output. Closed-loop control produced a visible and measurable improvement in the stability of the neutron flux output over time. This also reduces operator interaction with the High Energy Ion Beam Generator control system, thus reducing the potential for operator error.

Open loop control is used to bring the system up to an initial neutron flux setpoint, after which closed loop control is activated. Control gains are determined based on the selected neutron flux setpoint to ensure closed loop control over a smaller operating envelope. While closed loop control is active, additional limits are added to the control authority in the form of maximum and minimum HVPS setpoints for a given neutron flux setpoint.

The physics of neutron generators is nonlinear when considered over the mechanical operating regime, encompassing five orders of magnitude of neutron output. The mechanics of the beam scraper, where a circular beam impinges on a flat plate with straight edges, allowing part of the circular beam to pass through, further contributes to the nonlinearity of the control problem.

A linear control strategy was applied to the system by implementing operation over a small linear portion of the system's operating envelope. Traditional control loop tuning methods can then be applied to generate gains specific to each operating point. Control of the HVPS setpoint was active, but the scraper position was held at steady state and vice versa. This removed the nonlinearity inherent in the scraper motion from the control problem.

Closed loop control of neutron flux output via control of beam scraper position was successful but did not work as well as control of the HVPS set point. The ability of the beam scraper position to control flux output was dependent on the initial position of the scraper. The use of a linear control algorithm to set the position, which has a nonlinear effect on flux output, was not selected as optimal in favor of applying a linear control loop using the HVPS voltage as the controlled variable.

Additional features of the control system include, but are not limited to, auto-tuning algorithms to accelerate the development of control gains, dynamic signal analysis of the physical system in either open or closed loop form, modeling the open loop neutron generator system based on first principles, enabling state space or pole-placed control algorithms, full system simulation to enable hardware-in-the-loop (HIL) methods for selecting a control strategy, fuzzy logic control algorithms to enable bumpless transfer between operating regimes, and generation of protocols to enable fully automated operation of the neutron generator system, including automatic start-up, turn-off, and error handling.

E. Closed Loop Control for Beam Current
The specific application of a particle accelerator for ion implantation requires the beam current to be maintained within +/- 1% of the current set point. Multiple signals are required to calculate the beam current, including the high voltage power supply current, the extraction power supply resistor divider drain current, and current losses due to cooling water leaks. Real-time calculation of the beam current from these signals is performed by the control system. Open loop control by a skilled operator is insufficient to ensure that the beam current output remains within the required accuracy due to the multiple variables that affect the system dynamic.

VI. EXEMPLARY USES
(A. Thermal Neutron Radiography)
Neutron radiography and tomography are proven techniques for non-destructive testing of manufactured components in the aerospace, energy, and defense sectors. It is currently underutilized due to the lack of accessible high-flux neutron sources. Like x-rays, when neutrons pass through an object, they provide information about the internal structure of that object. X-rays interact weakly with elements of low atomic number (e.g., hydrogen) and strongly with elements of high atomic number (e.g., metals). As a result, their ability to provide information about low-density materials is very poor, especially when in the presence of higher density materials. Neutrons do not suffer from this limitation. They can easily pass through high-density metals and provide detailed information about the interior low-density materials. This property is crucial for several components requiring non-destructive evaluation, including composite materials such as engine turbine blades, munitions, spacecraft components, and wind turbine blades. For all of these applications, neutron radiography provides crucial information that x-rays cannot provide. Neutron radiography is a complementary non-destructive evaluation technique that can provide the missing information.

Phoenix Nuclear Labs (PNL) designs and builds high yield neutron generators that drive subcritical assemblies developed by SHINE Medical Technology to produce the medical radioisotope Molybdenum-99 (abbreviated "moly"). In some embodiments, such systems are adapted and modified for neutron radiography indications. In some embodiments, the systems include one or more of the features described in Sections I through V above to provide efficient, cost-effective, robust, safe, and easy-to-use neutron generation. In some embodiments, the systems are further modified as described below.

The neutron generator used in this embodiment is originally designed for the production of medical isotopes and therefore requires a relatively high neutron yield. The amount of neutron radiation generated exceeds acceptable levels for nearby personnel, and therefore the radiation-generating portion of the device should be installed underground. Because part of the device is then underground, there is very limited space in which to construct the radiography system.

The neutron yield of a PNL generator is very high for its size and cost, but several orders of magnitude lower than a typical neutron radiography facility, e.g., a nuclear reactor. Therefore, the neutron detection medium should be in close proximity to the neutron source. Conversely, in a nuclear reactor, it is typical for the detection medium to be several meters away from the neutron source, allowing space to install filters to mitigate undesirable types of radiation, primarily stray gamma rays, that would partially blur the image during acquisition.

For PNL systems, the close proximity of the neutron detectors results in a large gamma radiation flux, which generally decreases with the inverse square of the distance from the source, while precluding the use of sufficient gamma filtering materials such as lead or bismuth, which is exacerbated by the limited space available underground in PNL systems.

The PNL system uses deuterium-deuterium fusion to generate neutrons and does not produce gamma rays in the initial reaction. Subsequent reactions between the neutrons and the surrounding material are of interest. The radiography setup has a neutron guide (e.g., collimator) that is layered on the inside with a cadmium sheet, a highly neutron absorbing material. This ensures that neutrons that are not aimed directly at the detector will essentially be filtered out of the beam. Two gold foils are employed, in some embodiments one is coated with cadmium to simulate standard neutron activation analysis techniques and determine the composition of thermal and fast neutrons in the beam. However, the cadmium emits 550 keV gamma rays after the neutron absorption process. This gamma radiation can strike the detector and cause some clouding of the image. This is an unavoidable process and should be reduced as much as possible.

Outside the neutron guide (e.g., collimator), there is a very large neutron population consisting of a spectrum of energies from 0 to 2.45 MeV. Generally, it is desirable to reduce the energy of the neutrons as much as possible, since low energy neutrons are used in the imaging process. However, these low energy neutrons are more likely to generate subsequent gamma rays when absorbed by the surrounding material, as in the case of cadmium. The low energy neutrons cause these gamma production events regardless of whether they are inside or outside the neutron guide. Since only the neutrons inside the guide are useful for image collection, the neutrons outside the guide must also be absorbed. This is accomplished here by a layer of borated polyethylene (BPE), which absorbs the neutrons before they can cause a gamma production event in the cadmium. However, boron emits 478 keV gamma rays, which can be easily absorbed by a layer of lead between the BPE and the neutron guide wall. In some embodiments, the borated polyethylene (BPE) on the collimator is conical in shape, runs the length of the collimator (e.g., about 40 inches), and is 1 inch thick. The BPE on the imaging box where the images are collected is rectangular in shape, surrounds the box on all sides except for the opening where the collimator end is, and is also 1 inch thick.

Some neutrons can traverse the borated polyethylene and still produce gamma events in the cadmium. These are known as epithermal neutrons and should also be mitigated. To slow these neutrons down to an energy that allows for absorption, a 6-inch layer of high density polyethylene (HDPE) is added surrounding the layer of BPE. In some embodiments, the HDPE layer is 4-8 inches thick. The HDPE layer assists in mitigating the epithermal neutrons to thermal energy such that they are absorbed by the boron in the BPE without even reaching the cadmium layer. Additionally, a diffusion region of air is introduced that allows relatively the same optical path length for thermal neutrons to enter the collimator aperture while increasing the distance that fast neutrons must traverse before entering. In some embodiments, the air diffusion region is 6 cm long and 2.5 cm in diameter. This longer path length for the fast neutrons allows them more opportunity to scatter within the moderating medium and thus be moderated to more thermal energy. Although alternative materials such as water and graphite can be used in place of HDPE, HDPE provides a more cost-effective material that can be easily machined.

Finally, the collimator is offset so that it does not "point" directly at the fast neutron source. This ensures that what the collimator is "targeting" is rather the thermal neutron population, which will reduce the fast neutron content through the aperture. In some embodiments, the collimator is offset both radially and tangentially from the neutron source since it does not have a direct line of sight to the neutron source, and also to place moderating material between the collimator aperture and the neutron source. In some embodiments, this is offset 17 cm radially and 14 cm tangentially. The location is found by observing where the highest population of thermal neutrons is and then placing the collimator aperture in that area. The placement of the collimator then disrupts the population. Further offsets are performed to find a location that produces the highest thermal neutron population at the opposite end of the collimator.

The MCNP (Monte Carlo N-Particle) transport code is used to simulate neutron transport and gamma radiation generation from neutron capture in various materials. The simulations utilize a library of nuclear data from calculations and empirical data on scattered and absorbed radiation. Simulation packages have been available for decades and are continually updated and improved.

Various moderating materials, including light water, heavy water, and graphite, have been tested in an attempt to increase the available thermal neutron flux on the gold foil, reduce the fast and thermal exoflux on the foil, and reduce the gamma rays at the end of the collimator. Foil measurements are being attempted to verify that the model itself is centered on accurate predictions.

Optimization of the MCNP model has been performed to determine the optimal thickness of the HDPE, BPE, lead, moderator materials and geometry, as well as the diffusion region. This optimization has revealed a practical geometry in terms of size and weight. One major difficulty with such a highly shielded geometry is that the neutron transport through the collimator aperture is very low, about 7 orders of magnitude lower than the source production. To obtain sufficiently high counting statistics for accurate predictions, very long simulations have to be run or very judicious particle counting has to be performed.

The first test was performed using only graphite blocks as the moderating material with no BPE or HDPE on the outer layer of the collimator. It was then found that many fast neutrons could flow through the interstitial spaces between the graphite blocks, increasing the fast neutron population at the image plane. It was also recognized that thermal neutrons outside the collimator were generating a large population of gamma rays from the inner layer of cadmium due to the lack of shielding on the outside of the collimator.

Water was then added to the system to fill the cracks in the graphite and provide a 100% fully moderated system. However, because water is a relatively highly absorbing material for thermal neutrons, while the fast neutron flux dropped, so did the thermal neutron population.

A partial heavy water moderator was built into the graphite stack. Heavy water is both highly scattering and lightly absorbing of neutrons, making it an excellent moderating material. The thermal neutron population was found to increase, while the fast neutron population remained relatively constant. However, heavy water is very expensive, and the ideal configuration of this material for a moderator is impractical, especially as it does not sink in light water.

As described above, the fast and thermal neutron populations are so large and, in particular, so close together that they must be coupled together in the underground chamber. Due to this limitation, very carefully selected shielding must be used to both shield the thermal neutrons and thermalize the fast neutron population. The embodiments described herein achieve this result.

An example configuration is shown in FIG. 24 that provides a good solution for high heat/low fast neutron flux while reducing gamma population at the image plane. Optimization of all geometries should be performed to achieve optimal thickness of HDPE, BPE, lead, moderator material and geometry, as well as the diffusion region. For one designed system, it has been determined that a large heavy water vessel should be used surrounded by HDPE and BPE to optimize the moderator and shield the environment from unwanted radiation. This is configured as a ground system, but the image plane is still in close proximity to the neutron source. With this configuration, careful design as described herein is required to enhance the desired radiation characteristics while suppressing unwanted radiation such as gamma rays and fast neutrons.

(B. Semiconductor Processing)
The systems and methods described herein (e.g., using hydrogen ion particle accelerators) find application in semiconductor processing. Such systems find application, for example, in the formation of thin films of material from bulk substrates. The thin films of material are separated from the bulk substrate by creating a cleave region formed by particles embedded from a hydrogen ion particle beam and then cleaving at the cleave region. In some embodiments, the thin films are wafers used in the production of solar panels (e.g., solar grade photovoltaic (PV) wafers) or light emitting diodes (LEDs). The wafers can be any of any desired shape (e.g., circular, square, or rectangular). The wafers can be less than 100 micrometers thick. In some embodiments, the wafers have a thickness between 2 and 70 microns. In some embodiments, the wafers have a thickness between 4 and 20 microns.

Silicon wafers are traditionally produced by first creating a single crystalline cylindrical ingot of silicon (see, e.g., U.S. Pat. No. 9,499,921, incorporated herein by reference in its entirety). In one example, circular wafers are sliced from the end of the cylindrical ingot by a diamond-coated wire. The diamond-coated wire is typically about 20 micrometers in diameter. This method of producing wafers by slicing the wafers from the end of the cylindrical ingot produces waste of the thickness of the diamond-coated wire, or about 20 micrometers, by grinding that amount of thickness into dust. In another example, the crystalline cylindrical ingot is cut into squares or rectangles by squaring the ingot into an elongated rectangular box shape about 1.5 meters long. In the process of squaring the ingot, valuable material is removed as waste. Such waste and inefficiency can have significant impacts, as the cost of materials can dramatically affect the suitability of certain products and technologies.

The systems provided herein enable the production of desired semiconductor materials at a scale and efficiency previously unattainable due to their cost-effectiveness, efficiency, robustness, safety, and other desirable parameters, reducing overall manufacturing costs and facilitating an expanded market for such materials. The high energy ion beam systems described herein can be integrated into existing fabrication systems and processes as a hydrogen ion source. For example, existing systems that employ high energy ion beam generators integrated with wafer fabrication components can substitute their ion beam generators for those described herein. Examples of such systems are described in, but not limited to, U.S. Patent Application Nos. 2015/0340279, 2015/0044447, and 2016/0319462, U.S. Patent Nos. 7,939,812, 7,982,197, 7,989,784, 8,044,374, 8,058,626, 8,101,488, 8,242,468, 8,247,260, 8,257,995, 8,268,645, 8,324,592, 8,324,599, 8,338,209, 9,404,198, and 9,499,921, and in the SIGEN POLYMAX systems (see, e.g., Kerf-less wafer production, Sigen, Photon's 4th PV Production Equipment Conference (March 4, 2009)), SOITEC SMART CUT systems (see, e.g., www.soitec.com/en/products/smart-cut), and AXCELIS high energy implant systems in the PURION, OPTIMA, and PARADIGM SERIES systems (see, e.g., www.axcelis.com/products/high-energy, and Felch et al., Ion implantation for See, "Semiconductor Devices: The Largest Use of Industrial Accelerators," Proceedings of PAC2013, Pasadena, CA USA (the disclosures of which are incorporated herein by reference in their entirety).

All publications and patents provided herein are incorporated herein by reference in their entirety. Various modifications and variations of the described compositions and methods of the invention will become apparent to those of skill in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention that are apparent to those skilled in the art are intended to be within the scope of the invention.

Claims (9)

1. A neutron generator system, comprising:
a) an accelerator for generating an ion beam;
b) a gas target positioned to be contacted by the ion beam;
c) a target aperture separating the accelerator and the gas target;
d) a counter gas jet that increases the pressure differential across the target opening ;
The counter gas jet is positioned at the target aperture . The neutron generator system of claim 1, wherein the inverse gas jet includes a nozzle that converges and then diverges. The neutron generator system of claim 1, wherein the inverse gas injection comprises a narrow diameter gap, a plenum, and a nozzle having a nozzle opening. 4. The neutron generator system of claim 3 , wherein the nozzle opening of the reverse gas jet is 3/8 inch. The neutron generator system of claim 3 , wherein the narrow diameter gap of the reverse gas jet is less than 0.01 inches. 1. A method of increasing a pressure differential across a target opening of a neutron generator, comprising:
The method includes using a counter gas jet positioned at the target aperture;
The neutron generator includes:
i) an accelerator for generating an ion beam;
ii) a gas target and a gas aperture, the gas target being contacted by the ion beam, the target aperture separating the accelerator and the gas target. The method of claim 6 , wherein the counter gas jet comprises a nozzle that converges and then diverges. The method of claim 6 , wherein the counter gas jet comprises a 3/8 inch nozzle opening. The method of claim 6 , wherein the reverse gas jet comprises a narrow section gap of less than 0.01 inches.